Prepare rice according to package directions, omitting salt and fat, to make 4 cups cooked rice.
While rice cooks, slice steak in half lengthwise; slice each half diagonally across grain into 1/4-inch-thick slices. Combine chili powder, cumin, and salt in a zip-top plastic bag; add meat. Seal bag, and shake until meat is well coated.
Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add meat; stir-fry 4 minutes or until browned.
Remove meat from skillet, and set aside; wipe drippings from skillet with a paper towel. Coat skillet with cooking spray; place over medium heat until hot. Add pepper stir-fry; stir-fry 2 minutes or just until tender. Add tomatoes; bring to a boil. Cook 2 minutes, stirring occasionally. Return meat to skillet; cook until thoroughly heated. Remove skillet from heat.
Place 1 cup rice on each of 4 plates; top evenly with meat mixture.