Mix the flour and salt in a bowl. Pour in half of the milky water and oil, whisk until smooth.
Add the eggs along with the remainder of the milky water, whisk into a smooth batter. Cover and leave to stand at room temperature for approx. 30 mins.
Mix the spinach, ricotta, cheese and garlic, season.
To cook the omelettes
Heat a dash of oil in a non-stick frying pan (approx. 22 cm in diameter). Pour enough batter into the pan to thinly cover the base.
Reduce the heat. Once the underside is cooked and separates from the pan, turn the omelette and finish cooking. Transfer the omelette to a cooling rack. Repeat these steps with the remainder of the batter.
Layer the omelettes and spinach filling in the prepared tin, fill 1 layer with 3 tbsp of chopped tomatoes and a little cheese. Place the final omelette on top. Cover with the remainder of the tomatoes and cheese.
To bake Approx. 15 mins. in the centre of an oven preheated to 200°C. Remove from the oven, remove the tin frame, slide onto a plate and serve hot.