Melt 1 tablespoon butter spread in large nonstick skillet over medium-high heat. Add ground beef, season with salt and pepper, and cook until browned and crumbly, 5 to 7 minutes. Transfer to a bowl.

Melt remaining 1 tablespoon butter spread in same skillet over medium-high heat. Add bell pepper and onion and cook, stirring occasionally, until crisp-tender, about 5 minutes.

Stir in water, rice, and tomato; increase heat to high and bring to a boil. Reduce heat, cover, and simmer until rice is tender, about 7 minutes. Stir in beef and cook until heated through.

Spoon beef and rice mixture into taco shells and serve.