Preheat the oven to 200°C (400°F) and line a large baking dish or sheet with parchment paper.
In a mixing bowl, combine 2 minced garlic cloves, 1/2 tablespoon cumin, 1 teaspoon smoked paprika, 1/2 teaspoon salt, 1/2 teaspoon pepper, the juice of 1 large lemon, and 2 tablespoons olive oil to make the marinade.
Add the 2 pounds of skinless chicken thighs to the marinade and toss until each piece is fully coated.
Arrange the chicken thighs in a single layer on the prepared baking dish and roast in the preheated oven for 30–35 minutes, or until an instant-read thermometer inserted into the thickest part reads 165°F (74°C).
While the chicken roasts, make the green sauce: add 1 cup cilantro, 1 small chopped jalapeño, 1 clove minced garlic, 1 tablespoon olive oil, 1 tablespoon lemon juice, 1/4 teaspoon salt, and 1/2 cup sour cream to a blender or food processor and blend until smooth.
When the chicken is done, remove it from the oven and let it rest for 5 minutes.
Serve the chicken drizzled with the cilantro-jalapeño green sauce.
