Preheat the oven to 400°F / 200°C. Line a baking dish with parchment paper or lightly grease it.
Mix 3 tablespoons tomato paste, ½ teaspoon kosher salt, 1 tablespoon lemon juice, and 1 tablespoon extra virgin olive oil in a large bowl.
Pat 750 g boneless skinless chicken thighs dry with paper towels. Add them to the tomato paste marinade and coat each piece evenly.
Arrange the chicken thighs in a single layer in the prepared baking dish. Spread any remaining marinade over the top.
Bake for 20–25 minutes. Check the thickest part with an instant-read thermometer. Remove the chicken when it reaches 165°F (74°C).
Rest the chicken for 5 minutes before serving.
Notes
Optional marinating: For deeper flavor, coat the chicken and refrigerate it for 10–15 minutes before baking. This optional time is not included in the total time.Check the size: Chicken thighs vary in thickness, so begin checking their temperature after 20 minutes to prevent overcooking.Leave space between the pieces: Arrange the thighs in one layer without crowding so they roast instead of steaming.