Fry the onion and garlic in fine cubes in a little butter or oil in an oven-safe pan until light yellow. Add the selected, washed spinach, cover and let collapse (approx. 1 minute). Spread the ravioli on it. Put in the oven at 170 °.
Meanwhile, prepare the béchamel: melt the butter, stir in the flour until smooth and sweat briefly, pour on cold milk or broth while stirring with a whisk, simmer for a good minute, stirring. Season to taste with granulated broth and sea salt, not too strong, as the cheese also has salt. Dice the tomatoes.
Take the pan out of the oven, spread the coarsely grated cheese, herbs, seeds and diced tomatoes on the Maultaschen, pour the bechamel over them and bake in the oven until golden brown.