Begin by bringing a pot of water to a boil for the pasta. Once the water is boiling, add the pasta and cook until tender, which will take about 7 to 10 minutes. Be sure to reserve approximately half a cup of the starchy pasta water before draining the pasta in a colander.

While the pasta is boiling, heat a large skillet over medium heat and add the bacon. Cook the bacon until it becomes brown and crispy, then remove it with a slotted spoon and place it on a paper towel-lined plate to drain. Drain most of the bacon grease from the skillet, leaving roughly 2 tablespoons behind.

As the bacon cooks, finely chop the onion. Add the diced onion to the skillet with the remaining bacon grease and sauté for about 5 minutes, or until it softens and becomes translucent.

Stir in the frozen peas and add about a quarter cup of the reserved pasta water to the skillet. Cook the mixture, stirring occasionally, until the peas are heated through.

Add the drained pasta to the skillet and toss everything together until well combined. Remove the skillet from the heat.

Finish the dish by topping the pasta with grated Parmesan, salt, pepper, and crumbled bacon. Stir to combine all ingredients. Taste and adjust seasoning with additional salt and pepper as needed.