Bring a large pot of salted water to a rolling boil over high heat. Add your pasta and cook according to package instructions until al dente, about 8-10 minutes. Reserve about a cup of pasta water, then drain in a colander.

In a large skillet, heat olive oil over medium heat. Add the chopped onion and sauté for 3-4 minutes until translucent. Next, stir in garlic and sauté for another 1-2 minutes until fragrant.

Lower heat to medium-low and carefully pour in heavy cream. Stir gently into the sautéed onions and garlic. Gradually add in the grated pepper jack cheese, stirring continuously until melted completely.

Sprinkle in chili powder and black pepper to taste, stirring to incorporate. Allow the sauce to simmer for 2-3 minutes, thickening slightly. Taste and adjust seasoning as needed.

Add the drained pasta into the skillet with the sauce, tossing gently until well-coated. If sauce is too thick, add some reserved pasta water to reach desired creaminess.