Reduce heat to low. Stir in cream cheese, skim milk, cheddar/parmesan, Greek yogurt, lemon juice, and spices. Mix until smooth and creamy.
4 oz low-fat cream cheese, 1/2 cup skim milk, 1/2 cup nonfat shredded cheddar, 1/2 cup nonfat plain Greek yogurt, 1 tbsp lemon juice, 1/2 tbsp garlic powder, 1 tsp onion powder, 1/2 tsp salt, 1/2 tsp black pepper