Lidl's tomato sauces are all nice, particularly the one with chilli (it's not overly spicy). You can just stir them in or perhaps add some fresh roast veg as PP says.
Or do you like pesto? I like it again with fresh roast Mediterranean veg (I'm veggie) or DH likes with crispy bacon or pancetta pieces. Is you do like it, it's super easy to make a batch at the weekend (just blend pine nuts, fresh basil, parmesan (or veggie hard cheese for veggies) and some olive oil together, it keeps for at least a week in the fridge so we usually have some on standby for lazy nights (or we just buy jars if we CBA or don't have the fresh ingredients to hand, you can buy lots of different flavours in the jars like sundried tomato which is nice).
YY to fresh filled tortellini too, DH likes them with a tomato sauce but I usually just have with olive oil and some grated hard cheese...
For a quick cheesy sauce, I just cook the pasta, drain and return to the hot pan it came from, add in any veg/meat wanted (children usually like ham and peas!) then stir some marscapone or ricotta or sometimes Philly cream cheese in. The hot pan and pasta melts the 'sauce' a bit, you can even keep the pasta cooking water and add a spoonful or so in to loosen it up proper Italian style - although I'm sure a real Nonna wouldn't be using Philly
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Nigella has a recipe for marmite spaghetti, I've never tried it but could be good? www.nigella.com/recipes/spaghetti-with-marmite