Chop the onion. Put it in a bowl with lemon, vinegar and sugar. Mix. Marinate for 5 to 10 minutes.
Cut the zucchini in half lengthwise.
On your griddle or stove at maximum temperature, heat a large drizzle of oil. Cook the zucchini until it is slightly burnt on both sides (it must remain crispy on the inside). This can be done on the barbecue. Cut the zucchini into large pieces.
Peel the grapefruit and cut it into small pieces.
Place the courgette on a plate. Salt. Arrange the grapefruit wedges, a few pieces of onion, the burrata in pieces, sprinkle with oregano, salt, pepper, drizzle with olive oil. Finish the dressing by placing pieces of basil leaves.