Press chili powder evenly onto all surfaces of beef pot roast. Heat oil in stockpot over medium heat until hot. Place pot roast in stockpot; brown evenly. Pour off drippings.
Add tomatoes; bring to a boil. Reduce heat; cover tightly and simmer 2 to 3 hours or until roast is fork-tender.
Remove roast; keep warm. Skim fat from cooking liquid. Return liquid to stockpot; bring to a boil. Cook 8 to 10 minutes or until sauce is reduced to 2 cups.
Carve roast into thin slices; top with sauce.
Tip: One tablespoon chopped chipotle peppers in adobo sauce may be substituted for chipotle chili powder. Rub peppers evenly onto all surfaces of roast as above.