In a large bowl, combine the boneless chicken thighs, Greek yogurt, lemon juice, minced garlic, grated ginger, garam masala, and salt. Mix until well coated, then cover and refrigerate for at least 30 minutes; overnight for deeper flavor.

In a heavy-bottomed pan, melt 2 tablespoons of butter over medium heat. Add the finely chopped onions and sauté for 6-8 minutes until golden, then stir in additional minced garlic and ginger, cooking for 1-2 minutes.

Stir in 2 tablespoons of tomato paste and cook for a few minutes. Add crushed tomatoes, paprika, and cayenne pepper, reduce heat to low, and let simmer for 10-15 minutes until thickened.

Add the marinated chicken and any remaining marinade to the pan, stir to coat, and cook for 10-12 minutes until tender and cooked through.

Temper the heavy cream by whisking in a small amount of the hot sauce, then stir it back into the pan until achieving a rich and silky consistency.

Remove from heat, sprinkle with fresh cilantro, and serve immediately with naan or basmati rice, offering lime wedges on the side.