If possible, prep the pickled onions the night before. This isn’t necessary, even 30 minutes ahead works great, but you will get the brilliant pink color from an overnight soak. Thinly slice the red onion and add to a bowl with 1 teaspoon salt, 1 teaspoon sugar, 75g vinegar, and 75g water. Mix and let sit in the fridge.
Remove the green stalks from the fennel and slice the white section as thinly as possible. Put in a bowl with 1 teaspoon salt and a drizzle of olive oil. Mix.
Peel the oranges and slice into rounds. Place flat on a plate, then pile the fennel on top.
Cut the burrata into pieces and place on top of the oranges and fennel.
Add a layer of pickled onions, then sprinkle over chopped pistachios and flaky salt.
Finish with another drizzle of olive oil.
