Preheat oven to 400°F. Rinse scallops with cold water and pat dry. Place on plate and refrigerate uncovered.
Preheat ovenproof, nonstick sauté pan over medium heat. Add 1 teaspoon avocado oil and heat 10 seconds. Add onions and cook 2 minutes or until translucent, stirring constantly. Add garlic, salt, and ¼ teaspoon pepper.
Cook 1 minute, stirring constantly. Add tomatoes and chicken stock, and place pan in oven. Cook 10 minutes.
With 4 minutes remaining for sauce, remove scallops from refrigerator. Preheat second nonstick pan over medium-high heat. Add remaining 1 teaspoon avocado oil and heat 10 seconds. Sprinkle remaining ¼ teaspoon pepper over both sides of scallops. Place scallops in pan and press down lightly. Cook 45 seconds. Flip scallops, repeat process. Remove pan from heat and set aside.
Remove sauce from oven and stir in lime juice and cilantro. Divide sauce between 2 serving plates and place 2 scallops on each plate.