In a bowl, toss steak with cumin, salt, chili powder and red pepper flakes. Select saute setting on a 6-qt. electric pressure cooker. Adjust for medium heat; add oil. When oil is hot, brown meat in batches and remove. Add water, lemon juice and garlic to cooker; stir to loosen any browned bits. Press cancel. Return beef to cooker. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 20 minutes., Allow pressure to naturally release for 10 minutes, then quick-release any remaining pressure. Remove steak with a slotted spoon; keep warm., Add red pepper and onion to cooker. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 5 minutes. Quick-release pressure. Serve vegetables and steak with tortillas and desired toppings.