Shrimp Fajitas

In a medium bowl, whisk together olive oil, lime juice, cumin, and chili powder. Reserving about 1/4 cup marinade, pour the rest into a resealable plastic bag with the shrimp. Marinate shrimp for 15 minutes. In a large skillet over medium high heat, heat vegetable oil. Add bell peppers and onions and season with salt and pepper. Cook, stirring often, until vegetables are tender, about 5 minutes. Stir in jalapeño and garlic and cook for another minute. Remove vegetable mixture from skillet. Shake off excess marinade from shrimp and add to hot skillet in a single layer. Season with salt and pepper and cook until pink on both sides, 1 to 2 minutes per side. Add reserved marinade and let simmer for about 1 minute. Remove from heat. Serve shrimp warm with vegetable mixture over corn tortillas. Garnish with cilantro and cotija cheese, if desired.