In a bowl or large zipper-lock plastic bag, combine yogurt, lemon juice, ginger, 2 teaspoons cumin, cinnamon, cayenne pepper, 1 teaspoon salt, and 2 teaspoons pepper.
Add chicken and mix until evenly coated. Refrigerate at least one hour or overnight.
To make the sauce:
In a large skillet melt butter over medium-high heat until the foaming subsides. Stir in jalapeño and garlic until fragrant, about 30 seconds.
Add remaining cumin, paprika, and 1 teaspoon salt. Stir in tomato sauce and heavy cream. Bring to a boil; reduce heat and simmer uncovered for 20 minutes, until sauce has thickened.
To grill the chicken:
Thread chicken evenly on 4 skewers, discarding excess marinade. Lightly oil grill and preheat over high heat.
Grill chicken until the internal temperature of the largest piece registers 165°F on a thermometer, about 5 minutes on each side. Transfer to a platter and tent with foil until the sauce has thickened.
Add the chicken to the sauce and stir until heated through, about 10 minutes longer. Serve the chicken with sauce over rice, garnished with cilantro if desired.