Rub the boneless skinless chicken breasts with taco seasoning. Heat the cast iron skillet with olive oil over medium-high heat until shimmering, about 1 minute, then lay the chicken in the pan with the first sizzle immediately noticeable.

Sear the chicken for 5-6 minutes per side until cooked through to 165°F. Flip only once, and watch for deep browned edges like a blackened crust before turning.

Remove the chicken and rest it briefly, then slice. When sliced, the center should stay juicy with no pink, and the juices should run clear.

Melt butter in a saucepan over medium heat, then whisk in all-purpose flour for 1 minute. The mixture should turn smooth and lightly golden and look glossy, not dry.

Gradually add whole milk while whisking until smooth. Keep whisking until the sauce base looks silky with no floury lumps.

Stir in shredded Mexican cheese blend and Velveeta until fully melted. The texture should become thick and elastic, pulling slightly as it melts.

Add diced tomatoes with green chiles (Rotel), jalapeño, and cumin, then simmer for 3-4 minutes until smooth and thick. The sauce should look vibrant orange and coat the spoon with a glossy sheen.

Plate the sliced chicken and pour the cheese sauce generously over the top. Make sure each piece is covered so the queso forms an even pool in the plate center.

Garnish with fresh cilantro and lime wedges. Finish with a bright green-citrus contrast so the surface looks fresh and inviting.