In a large heated skillet, add the olive oil and the butter. Once the butter is melted, add the diced onion, salt, and pepper. Cook until the onions are translucent and brown around the edges. When ready set aside. Now we will boil the pasta.
Bring a large pot of salted water to a rolling boil. Add the pasta and cook until al dente (about 10 minutes).
Right before the noodles have finished cooking, add the frozen peas in with the pasta. Cook in the same seasoned water for about two minutes.
When ready, drain the pasta and peas. Transfer the pasta and peas in with the onions. Toss and mix to combine.
Add the parmesan cheese and mix.
Serve right away with extra cheese and cracked black pepper on top.