Pat the chicken breasts completely dry with paper towels. Rub the meat generously on all sides with the taco seasoning and kosher salt.

Heat a matte black cast-iron skillet over medium-high heat. Add olive oil. Carefully lay the chicken in the skillet and leave it completely undisturbed for 6-7 minutes. Flip only when a deep golden-brown crust has formed and internal temp reaches 165°F (74°C). Remove the chicken to a plate.

Lower the heat to medium-low. Melt the butter directly into the residual chicken drippings. Whisk in the flour, cooking for exactly 1 minute until it smells lightly nutty.

Slowly pour in the whole milk while whisking constantly. Continue to gently simmer and whisk until the mixture thickens enough to coat the back of a spoon, about 3-4 minutes.

Remove the skillet entirely from the heat. Slowly sprinkle in the freshly shredded sharp yellow cheddar cheese, whisking continuously until you achieve a thick, creamy yellow queso cheese sauce.

Return the rested chicken breasts back into the cast-iron skillet. Spoon the glossy melted cheese sauce generously over the top.

Scatter the diced bright red tomatoes and diced green chiles over the smothered meat. Finish by delicately dropping the freshly chopped green cilantro leaves across the top.