1. Mix the flour, yeast and salt in a large mixing bowl.
2. Pour in the water and olive oil. Stir everything together with a large wooden spoon. If you own a cake mixer with a dough hook attachment, feel free to start off the dough in the mixer.
3. When the mixture has mosty stuck together turn the mixture out on to a work surface on bread board.
4. Knead the mixture for 10 minutes or until the dough is shiny and smooth. Put the dough into a large mixing bowl, coat it in a thin layer of olive oil and cover the bowl with a tea towel.
5. Leave this in a warm drafty place for between one and two hours, until it has doubled in size.
6. Once the dough has doubled in size, flatten and shape the focaccia in an oiled baking tin. Make sure you stretch it into the tin corners.
7. Press deep holes (all the way to the bottom) into the focaccia. Push the medley tomato halves (cut side up) into the focaccia.
8. Coat with olive oil and sprinkle with rosemary and salt.
9. Cover with tea towel and prove the focaccia in the tin for a further 30 minutes. Preheat your oven.
10. Bake for 10 minutes at 250°C, then turn the oven down to 200°C and bake for further 10-15 minutes until the top is golden brown.

Note: The baking tin used has the following dimensions 26cm x 19cm x 5cm