Bring a large pot of salted water to a boil and cook your pasta until al dente, according to package instructions. Before draining, reserve about ½ cup of pasta water—this will help create the sauce.

In a large skillet over medium heat, add olive oil and butter. Once the butter is melted, add in garlic and capers, cook for 2-3 minutes, until fragrant.

Reduce heat to medium-low heat and add in kosher salt, black pepper, lemon zest, heavy cream, and red pepper flakes. Stir to mix together and continue to cook for 5 minutes, until the cream begins is warmed throughout and begins to thicken, stirring frequently.

Add parmesan cheese and lemon juice and stir to combine. Add the cooked pasta to the skillet and toss it in the sauce. Slowly pour in about ¼ cup of the reserved pasta water to help everything coat the noodles beautifully (for a looser sauce, add all of the pasta water). Add more parmesan cheese, parsley, and pistachios on top.