In a large skillet, heat the olive oil over medium heat. Add the diced red onion and sauté for about 3-4 minutes until it becomes translucent. Next, toss in the diced red and yellow bell peppers, continuing to cook for an additional 5 minutes until they are tender and slightly caramelized.
Once your vegetables are ready, it’s time to add the star ingredients! Stir in the black beans, pinto beans, and red kidney beans. Mix well to combine all the flavors.
Sprinkle the taco seasoning over the bean and vegetable mixture. Squeeze in the juice of one lime and add the chopped cilantro. Stir until everything is evenly coated with the seasoning. Season with salt and black pepper to taste. Allow the mixture to cook for another 5 minutes to let the flavors meld beautifully.
While the filling is cooking, preheat your taco shells according to the package instructions. This usually takes just a few minutes in the oven and adds a delightful crunch to your tacos.
Once the shells are warm and the filling is ready, it’s time to assemble! Spoon the three bean mixture generously into each taco shell. Top with your favorite toppings such as shredded cheese, lettuce, chopped tomatoes, diced avocado, sour cream or Greek yogurt, and additional cilantro.