In a large bowl, combine yeast, sugar, and warm water. Whisk and set aside until foamy, approximately 5 minutes.

Add flour, salt, baking powder, and oil and mix well. The dough will be very wet. Cover with a damp tea towel and sit in a warm place in the kitchen for 60 minutes until doubled in size.

Oil and line a rectangular pan and place the mixture in, pressing it into the sides of the tin with oiled fingers.

Drizzle olive oil over the top and press your fingers into the dough to make divots on the surface. Sprinkle with sea salt and rosemary. Cover and leave aside to rise for a further 40 minutes. Preheat oven to 450ºF/220ºC

Bake 15-20 minutes until the top is crispy and brown.

Cool slightly before slicing.