Cut butternut squash into spirals using a spiralizer fitted with the large shredding blade.
Heat 2 tablespoons olive oil in a skillet over medium-high heat. Saute squash until slightly tender, about 3 minutes. Add taco seasoning; stir. Add black beans and tomatoes; cook and stir until beans are hot and tomatoes are soft, about 5 minutes more. Remove from heat.
Heat 1 tablespoon olive oil in a skillet over medium-high heat. Fry 1 tortilla at a time until lightly browned, about 30 seconds per side.
Place 1 tablespoon sour cream on each tortilla; add about 1/4 cup squash mixture and sprinkle with 1 tablespoon feta cheese. Top with lettuce and cilantro.