Combine sour cream, cilantro, lime juice, and jalapeno pepper in a food processor.

Process until smooth to make the jalapeno sauce.

Combine the jalapeno sauce and thinly sliced white onion in a small bowl and set aside.

In a separate bowl, combine paprika, brown sugar, dried oregano, garlic powder, salt, ground cumin, and ground red pepper.

Sprinkle the spice mixture evenly over both sides of the tilapia fillets.

Heat canola oil in a large cast-iron skillet over medium-high heat.

Add the tilapia fillets to the hot skillet.

Cook for approximately 3 minutes on each side, or until the fish is cooked through and flakes easily with a fork.

Warm the corn tortillas according to the package directions.

Divide the cooked tilapia evenly among the warmed tortillas.

Top each taco with the onion mixture and thinly sliced avocado.

Serve immediately with lime wedges for squeezing over the tacos.