Drizzle a nonstick skillet with olive oil and set on medium heat. Saute garlic, onion, bell pepper and tomatillo for about 8 to 10 minutes; do not let brown. Stir in black beans and spices to taste. Allow to cook for about 15 to 20 minutes; remove from heat.
Spoon black bean mixture onto warm tortilla. Sprinkle with cheese and garnish with lettuce and tomato. Makes about 10 to 15 tacos.