1 15-ounce can crushed tomatoes
1 medium onion, chopped
2 cloves garlic, chopped
2 tablespoons tomato paste
2 teaspoons garam masala (Indian spice blend)
kosher salt and black pepper
1 1/2 pounds boneless, skinless chicken thighs (about 8)
1/2 English cucumber, halved and thinly sliced
1/4 cup fresh cilantro leaves
1 tablespoon fresh lemon juice
1 cup basmati or some other long-grain white rice
1/2 cup heavy cream