Sort the spinach, wash well, drain and possibly cut smaller. Wash and halve the tomatoes. Wash basil, shake dry, remove leaves and chop coarsely.
Preheat the oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer) and line an ovenproof dish (approx. 20 x 30 cm) with baking paper. Whisk eggs and season with salt and pepper. Stir in spinach, tomatoes and basil. Pour into the mould. Distribute the ricotta in pieces on top. Bake in a hot oven for about 20 minutes.
Remove the frittata from the oven, lift it out of the pan with the help of the baking paper and cut it into pieces.