Sift the flour. Dissolve the yeast in cool water, add the rest of the ingredients and pour it all into the flour.
Knead a soft dough. Leave the dough to rise a bit. Roll out the risen dough into a thin layer. Put it in an oven dish laid out with baking paper.
Arrange tomato slices (thin ones) on top, as well as finely grated onions. Sprinkle with oil and bake in a preheated oven until golden.
Sprinkle the cooked foccacia with basil leaves.