Combine the wholemeal flour, plain flour and salt. Cut the butter into small pieces and work it into the flour with your fingers. Gather the dough gently with water and pat the loose dough into a tart dish (approx. 22 cm in diameter). Press the dough up the sides. Pre-bake in the middle of the oven approx. 15 min. at 200°C (conventional oven).
Brown the butter in a sauté pan. Sauté the onions over a medium heat for about 3 min. Distribute the onions In the pre-baked crust. Beat the eggs, then add the cottage cheese, thyme, salt and pepper. Pour the mixture over the onions and sprinkle with grated cheese. Finally, top with tomatoes and bake in the middle of the oven approx. 30 min. at 200°C (conventional oven).