Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add green onions and garlic; saute until tender.
Add black beans and next 4 ingredients; stir well. Bring to a boil; reduce heat, and simmer, uncovered until liquid evaporates, stirring frequently. Remove and discard lemon slice. Mash beans slightly with a poatato masher or a wooden spoon.
Arrange 3 spinach leaves on each tortilla. Spoon bean mixture evenly down the center of tortillas; sprinkle evenly with cheese. Roll up tortillas, place rolls, seam side down, in 13x9x2-inch baking dish coated with cooking spray.
Cover and bake at 350 degrees F. for 20 minutes or untiil thoroughly heated.
Place 1.2 cup shredded spinach on each individual serving plate. Top with 1 burrito. Sprinkle 2 Tbsp chopped tomato over each serving.