Strip the rosemary sprigs and chop half the leaves with a sharp knife. Place the kneading knife in the food processor and add the flour, yeast and chopped rosemary in the bowl. Mix everything together and pour 2 tablespoons of olive oil and 250 ml tepid water in a thin trickle through the feeding tube. Let the food processor run until the dough comes together. Then finish off by kneading it by hand for a few seconds on a floured surface. Shape into a ball and leave to prove in a bowl covered with cling film in a warm place for 1 hour, until it has doubled in volume.
Pre-heat the oven to 220°C. Shape the dough on the baking sheet into a 1 cm thick rectangle and make holes in it with a finger. Drizzle the remaining olive oil over it and place the tomatoes in the holes. Sprinkle with the rest of the rosemary leaves and the sea salt.
Bake the focaccia on the centre shelf of the oven for 15-20 minutes until golden. Leave to cool.