1. Heat oven to 450 degrees F. Coat a 13 x 9 x 2-inch baking dish with nonstick cooking spray.
2. In a medium-size pot, bring 2 1/4 cups water to a boil. Stir in rice and simmer, covered, on low for 20 minutes. Stir in tomatoes, chili powder, oregano and cumin. Simmer an additional 15 minutes or until rice is tender.
3. Meanwhile, fold fish in half skinned-side down and place in prepared dish. Cut lemon in half. Squeeze 1/2 of the lemon over inside and outside of fish. Mix together the mayo and cheese and spread evenly over the top of the fish. Bake at 450 degrees F. for 15 to 20 minutes or until fish flakes easily with a fork.
4. Serve fish with brown rice and spinach. Garnish with remaining lemon, sliced.