Burger King
Burger King Zesty Sauce Copycat Recipe
The onion ring dip. Horseradish, ketchup and mayonnaise, with a kick that arrives late. Five minutes and an hour in t…
How to Make Outback Steakhouse Bloomin' Onion Sauce at Home
The Horseradish Dipping Sauce, and How to Cut an Onion Into Petals
The sauce that makes the onion worth the effort, and the cuts that make the onion bloom.
AI-generated illustration created for food.fast. It is not photographic evidence of a prepared batch.
The Bloomin' Onion is theatre, and the dipping sauce in the middle of it is the part people actually reproduce. It is a horseradish mayonnaise with ketchup, paprika and a genuine amount of heat, and it is a close cousin of Burger King's Zesty sauce with more assertiveness.
The onion itself is a knife exercise rather than a cooking one, and this page covers it too - because a sauce for a dish nobody can make is not much use. It needs a sharp knife, a large onion and twenty minutes in iced water.
The sauce alone is worth making. It goes on a steak sandwich, a roast beef roll and a plate of chips, and it takes five minutes.
How this page shows its working
The method gives quantities, timings and observable cues rather than asking you to guess. The 4 cases in If it goes wrong explain likely causes and corrective action.
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How to cut an onion so it blooms
Take a large onion - the bigger the better, 350 g or more.
Cut the top off, about 1 cm down, leaving the root end completely intact. The root is what holds the whole thing together and cutting into it is the most common failure.
Peel it, then sit it cut side down.
Make 12 to 16 cuts from about 1 cm above the root, straight down to the board, spaced evenly around the onion like the spokes of a wheel. Start with four cuts at the quarter points, then subdivide each quarter twice. Even spacing matters more than exact count.
Turn it over and coax the petals apart with your fingers. Some will stick.
Twenty minutes in iced water. This is the step that makes it bloom - the layers absorb water, swell slightly and separate on their own. Take it out and the petals will be standing open.
Drain it upside down on a tea towel before it goes anywhere near batter.
How to make it, step by step
The sauce
-
Fold everything together and rest it an hour
Mayonnaise first, then everything else. Fold rather than whisk. An hour in the fridge for the powders to hydrate and the horseradish to distribute.
About 5 min
The onion
-
Cut and bloom it
Top off, root intact, 12 to 16 radial cuts stopping 1 cm above the root. Then twenty minutes in iced water until the petals stand open.
About 25 min -
Season the flour and set up the dredge
Flour with all the spices whisked through, in a wide bowl. Milk and beaten eggs in another.
About 3 min -
Flour, milk, flour - working it into every crevice
Dip the onion into the flour and turn it, pushing flour down between the petals with your fingers. Then the egg mixture. Then flour again, working it in properly. Shake off the excess.
TipThis is fiddly and it is the whole thing. Unfloured crevices come out pale and soft.About 8 min -
Fry at 175 °C, cut side down first, for 3 minutes
A whole onion displaces a great deal of oil, so fill the pan no more than a third and lower the onion in petals-down with a spider, away from you. Three minutes, then turn it with two spoons and give it another three to four. Read the frying safety guide first if you have not fried before - this is one of the bulkier things on this site to put into hot oil.
TipNever move a pan of hot oil, and keep a lid within reach. Let it cool completely in the pan afterwards.About 8 min -
Drain on a rack, salt, and serve with the sauce in the centre
Cut a hollow in the middle with a small knife and sit the sauce pot in it. Eat it immediately - it softens fast.
About 2 min
The air fryer version, which is genuinely worth doing
A whole bloomed onion is a lot of oil for one starter. The air fryer version is much more practical and surprisingly good.
Prepare and dredge exactly as above, then spray it generously with oil - go around it several times, getting into the petals - and cook at 190 °C for 22 to 25 minutes, spraying again at 12 minutes.
It comes out drier and less uniformly golden than the fried version, and the petals are crisper at the tips and softer at the base. For a Tuesday it is the right call, and it uses about two tablespoons of oil instead of a litre and a half.
Ways to change it once you have made it once
Air fryer
190 °C for 22 to 25 minutes, sprayed generously with oil twice. Much more practical.
Blooming cauliflower
A whole small cauliflower, cut the same way, parboiled for four minutes first. Excellent and much easier to handle.
As a steak sauce
The sauce alone, thinned with a teaspoon of lemon juice, on a steak sandwich. This is its best non-obvious use.
What went wrong, and how to fix it
Each entry names a likely cause as well as a correction, so the advice remains useful when equipment, ingredients or batch size differ.
The onion fell apart
- Why it happened
- The cuts went into the root.
- What to do
- Stop every cut a full centimetre above the root end.
The petals would not open
- Why it happened
- No iced water soak, or the onion was too small.
- What to do
- Twenty minutes in iced water, and use an onion over 350 g.
Pale and soft between the petals
- Why it happened
- Flour did not reach into the crevices.
- What to do
- Work the flour in with your fingers rather than shaking the bowl.
The sauce has no kick
- Why it happened
- A mild or old jar of horseradish.
- What to do
- Another tablespoon. Horseradish loses potency in an open jar.
Questions people actually ask about this recipe
How do I cut a Bloomin' Onion?
Top off, root intact, 12 to 16 radial cuts stopping a centimetre above the root, then twenty minutes in iced water.
Why does it need iced water?
The layers absorb water and swell, which separates the petals on their own.
Can I make it in an air fryer?
Yes - 190 °C for 22 to 25 minutes, sprayed generously with oil. Drier than fried and much more practical.
Is the sauce the same as Burger King's Zesty sauce?
They are close relatives. This one is more assertive - more horseradish, more cayenne and oregano.
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