Chop the tomatoes into a mixture of slices and wedges, then put them in a bowl. Toss with 1/2 tsp salt and the sugar, then leave to marinate for 30 mins. Meanwhile, bring a pan of water to the boil and add the broad beans. Boil for 2 mins, then drain and allow to cool for a couple of mins. Peel them out of their shells. This is a bit fiddly but well worth it – I use my thumbnail to pierce the skin, then gently squeeze out the shiny green beans.
Finely chop the herbs, then tip into a bowl and whisk in the olive oil, mustard, fennel seeds, most of the lemon zest, and red wine vinegar. Season, then stir in the broad beans.
Tip the tomatoes onto a serving platter. Top with the burrata, then spoon over the broad bean salsa. Scatter over the hazelnuts and remaining lemon zest to serve.