Combine yogurt, garlic, ½ teaspoon salt, spices, and lemon juice in a medium bowl and whisk well. Stir in chicken cubes, cover, and marinate for 2-24 hours.
Melt 2 tablespoons of butter in a large skillet over medium-high heat, then add half of the chicken to the skillet. Cook until browned, about 5 minutes, flipping occasionally. Remove to a plate and repeat with remaining chicken, adding butter if necessary. Remove chicken from skillet to a bowl and set aside.
Turn the heat down to medium-low and add 2 more tbsp of butter. Add the sliced onions and allow to cook, stirring occasionally, until very tender and slightly caramelized, about 10 minutes.
Melt remaining butter (2 tbsp), then stir in jalapeno (if using), cauliflower rice, and season with remaining salt. Cook, stirring until cauliflower rice is tender and any liquid has evaporated, about 5-7 minutes.
Add the chicken and fresh cilantro into the skillet and combine, heating through the chicken, about 2 minutes.
Serve immediately with a garnish of fresh cilantro. Enjoy!
<b>Note:</b> The chicken on it's own is also a great recipe to meal prep and add to salads or quickly cook up another side of veggies for lunch/dinner if you don't want to make the entire recipe!