In a small bowl, combine ¼ cup olive oil, minced garlic, 1 tablespoon lime juice, Cajun spice, and salt. Mix well to create the marinade.

Slice the bell peppers and onion into uniform ⅓-inch thick strips. Place them in a medium bowl and pour half of the marinade over them. Toss gently to coat all pieces evenly. Set aside to let flavors meld.

Pat dry the shrimp with paper towels to remove excess moisture. Place them in a separate medium bowl and add the remaining half of the marinade. Stir to coat the shrimp thoroughly and allow them to marinate briefly.

Heat a large heavy skillet or pan over medium heat and add ½ tablespoon of olive oil. When the oil is hot, add the shrimp in a single layer. Sauté for 1-2 minutes on each side until the shrimp are cooked through, opaque, and no longer translucent. Remove shrimp from the pan and transfer to a plate to avoid overcooking.

In the same pan, add the marinated bell peppers and onions. Sauté them over medium heat, stirring occasionally, for about 10 minutes or until they become soft and develop golden-brown edges. Then, turn off the heat.

Return the cooked shrimp to the pan with the sautéed vegetables. Add the chopped cilantro and squeeze 2-3 teaspoons of fresh lime juice over the mixture. Toss gently to combine all ingredients. Serve the shrimp fajitas hot alongside warmed or toasted flour tortillas, sliced avocado, jalapeño ranch, and lime wedges for squeezing.