1. 1. Season the beef tenderloin steaks with taco seasoning mix on both sides.

2. 2. Heat a skillet over medium-high heat and cook the steaks until desired doneness, about 4-5 minutes per side for medium-rare.

3. 3. In a separate pot, cook the rotini according to package instructions until al dente.

4. 4. In the same skillet used for the steaks, sauté the diced onions and bell peppers until they are tender and slightly caramelized.

5. 5. Slice the beef tenderloin steaks and serve them over the cooked rotini with the sautéed onions and bell peppers on top.

6. 6. Enjoy your delicious taco seasoned beef tenderloin with rotini!