In a bowl, combine ¾ cup (175 mL) of the yogurt, the tikka paste and lime zest; add chicken and stir to coat well. Let marinate at room temperature for 10 minutes or cover and refrigerate for up to 4 hours.
In a large skillet, melt butter over medium heat; sauté onion, garlic and salt for 3 minutes or until starting to soften. Add sweet red pepper and sauté for 3 minutes or until softened.
Stir in tomatoes and bring to a boil, stirring occasionally. Reduce heat and boil gently, stirring often, for about 3 minutes or until slightly thickened.
Sprinkle cornstarch over chicken mixture and stir to combine. Add to skillet with peas, stirring well. Simmer, stirring often, for about 10 minutes or until chicken is no longer pink inside and sauce is thickened.
Meanwhile, in a small bowl, whisk ground cumin, lime juice and cilantro into remaining ¾ cup (175 mL) yogurt. Serve chicken in sauce on rice, topped with yogurt.