Place sweet potatoes in a one-quart saucepan with 2 cups of water. Bring the water to a boil, reduce the heat, and simmer until the vegetable is fork tender, about 2 to 4 minutes. Remove from heat.
Heat 1 tablespoon olive oil in medium non-stick skillet over medium high heat. Add onions, red and green bell peppers, stirring constantly until vegetables are tender, about 4 to 5 minutes. Remove from heat.
Warm tortillas for 10 to 15 seconds on each side on an ungreased pan.
To assemble the burrito, place baby spinach each tortilla. Layer on sweet potatoes, onions, and bell peppers.
Top with avocado, onion, cheese and a pinch of salt & black pepper.
Roll up sides and serve warm.