I do all sorts of variations...but mainly
Spinach and ricotta - layer of garlic fried sliced mushrooms. Pasta. Bechamel. Layer of ricotta mixed with lightly cooked (squeeze out xs liquid) spinach, parmesan, black pepper and nutmeg...you can beat an egg in too if you want..makes a different texture, and then another layer of pasta etc until you fill your dish. Sub the spinach for kale too. That's a nice one.
Roasted butternut squash as a layer and lots of bechamel is nice too.
When I'm tired I sometimes just use a ball of mozzarella on top in place of cheese sauce or bechamel sauce. Usually sprinkle some grated cheddar too.
But my go to one is just a pasta sauce with veg of choice usually onion, garlic, pepper, courgette, mushrooms, carrot.... celery optional, oregano, and I add red lentils and stir until translucency then tin of chopped tomatoes and let it simmer.
God I'm hungry now 😋