Mix together erythritol, salt, and ground pepper. Spray cut side of avocado with cooking spray.
Sprinkle avocado halves with salt mixture, reserving some for finishing.
Place Avocado, pit side down, on grill rack. Grill 1-2 minutes on each side, or until lightly charred.
Combine sour cream, cilantro, and lime juice.
Cut each avocado half in half. Drizzle with sour cream mixture and sprinkle with a little reserved sugar/salt/pepper mixture. Serve with flour tortilla.