Preheat oven to 220°C (top and bottom heat).

Wash the bell peppers, remove the cores and cut into large pieces. Peel the onion and garlic, and quarter the onion.

Place the vegetables on a baking sheet, season generously with salt, and toss with the oil. Roast in the oven at 220°C for 20 minutes, until the bell pepper skins begin to blister, the vegetables are soft, and a rich, roasted aroma has developed.

Meanwhile, bring a pot of water to a boil. Generously salt the water and cook the pasta in it. Drain the pasta one to two minutes earlier than indicated on the package, reserving some of the pasta water (approximately 30 milliliters or 2 tablespoons).

After 20 minutes, or when the vegetables have developed a nice roasted aroma, reduce the temperature to 200°C and remove the baking sheet from the oven. Place the vegetables, tomato paste, and cottage cheese in a blender or food processor and purée until smooth. Season with salt and pepper.

Pour the pasta sauce into a casserole dish. Add the spinach, pasta, and 30 ml of pasta water, and stir well. Sprinkle cheese over the surface and return the pasta bake to the oven for 10 minutes at 200°C (390°F) using conventional oven settings (top and bottom heat) until the cheese has melted.