Stir together curry, cumin, salt, ginger, cardamom, chili powder, and pepper in a small bowl.
Add chicken to a medium bowl; add spices, and toss to coat.
Heat oil in a medium skillet over medium-high heat. Add chicken to skillet; cook, stirring occasionally, until lightly browned, 5 to 7 minutes.
Add onion and garlic; cook, stirring occasionally, about 5 minutes more.
Stir in tomato paste; cook until fragrant, about 2 minutes. Add coconut milk; stir to combine.
Bring to a simmer; reduce heat to medium-low, and gently simmer until chicken is cooked through and onion is tender, about 10 minutes.
Taste, and add salt, if desired. Garnish servings with cilantro; serve with rice.