Separate the broccoli florets from the stem, blanch them in boiling water and rinse with cold water. Cook the noodles al dente. Peel, halve and slice the onion.
Mix the tomatoes, cream, water, chopped garlic, basil and parsley together. Season to taste with salt and pepper. Mix the pasta in a large baking dish with onion rings and broccoli florets and pour the sauce over them. Scatter cheese on top and distribute the pesto selectively.
Bake the casserole, covered with aluminum foil, at 200 ° C for 30-40 minutes until the liquid is completely absorbed / evaporated.