Melt butter in large nonstick skillet on medium heat. Add chicken, onion and lemon juice; cook and stir 10 minutes or until chicken is no longer pink.
Stir in paprika, minced garlic, garam masala and cumin; cook and stir 1 minute. Add tomatoes; mix well.
Mix cream, cornstarch and salt in small bowl until smooth. Gradually stir into skillet. Add red pepper to taste, if desired. Bring to boil. Reduce heat to low; stirring frequently, simmer 5 minutes or until slightly thickened.