This one-pot meal packs in the flavor with toasted pasta, sautéed onions, and spicy Italian sausage. The tangy lemon juice with the kick of the chiles adds freshness to the creamy and rich penne.
Bring heat to a simmer in a saucepan (do not boil). Keep warm over low heat.
Heat a large skillet over medium heat. Add 1 tablespoon oil to pan; swirl to coat. Add uncooked pasta; cook 5 minutes or until toasted, stirring frequently. The trick is to cook the pasta like risotto, which releases starch into the liquid that becomes the sauce. The toasting step adds nutty, rich character and adds creaminess.
Remove pasta from pan.
Add the remaining 1 tablespoon oil, onion, and sausage to pan; cook 4 minutes or until browned, stirring to crumble. Remove sausage mixture from pan. Reduce heat to medium-low. Return pasta to pan. Add stock, 1 cup at a time, stirring constantly until each portion of stock is nearly absorbed before adding the next (about 35 minutes total), stirring frequently. Stir in sausage mixture, lemon juice, chiles, salt, and cheese. Garnish with oregano, if desired.