1. Prepare spaghetti according to package directions. Set aside.
2. Lightly coat a large, deep skillet with cooking spray & heat over medium. Add beef, onion, cactus, pepper & garlic. Cook 10-12 minutes, crumbling meat, stirring occasionally until meat is cooked through.
3. In a medium bowl, whisk tomato paste & water until smooth. Add tomato mixture & carrots to skillet. Mix well. Reduce heat to low & cook 7-8 minutes.
4. Serve beef & vegetable mix over spaghetti, topped with cheese.