Pat roast dry. In small bowl, combine chili powder, cumin, salt and pepper. Rub into roast.

In large nonstick skillet, heat oil over medium heat; brown roast on all sides, then transfer to slow cooker. In same skillet, cook onion, carrots and garlic, stirring occasionally until softened, about 4 minutes. Stir in tomatoes and puréed chipotle; bring to boil. Pour over roast in slow-cooker. Cover and cook for 8 hours on low or until tender.

Place roast on cutting board and cover with foil. Remove cooking liquid and purée in batches in food processor until smooth. Remove 2 cups (500 mL) purée to saucepan. Stir cornstarch with water until smooth. Stir into saucepan and bring to boil over medium-high heat. Reduce heat and simmer for a few minutes or until thickened. Serve with slices of beef.

Tip: Use any leftover cooking liquid as a base for soup. If you have leftover roast, shred or chop it, moisten it with sauce and heat through. Place in a tortilla or taco shell and top with shredded cheese.