Slice the onions into half moons. Warm a splash of olive oil in a pan on a medium high heat + melt in 2 tbsp butter. Allow to foam + brown, stirring regularly (2-3 mins).
Add the onions + a large pinch of salt. Cook on a medium heat, stirring regularly + adding a splash of water if sticking, until golden, softened + caramelised (at least 20 mins).
Mince the garlic + finely chop the sundried tomatoes. Once the onions have begun to caramelise (20 mins), add the garlic + tomatoes. Stir to combine + sauté for a further minute or two. Season with black pepper.
Get your pasta onto boil in salted water.
Pour in the cream + Parmesan cheese. stir well to combine.
Once your pasta is al dente, drain (reserving some pasta water) + add to the sauce with a ladle of pasta water. Stir + toss well to create a thick, glossy sauce.
Finely chop the parsley + add to the pasta, mixing well.
Season to taste + serve into bowls.
