Preheat oven to 375 degrees.
Cut top of garlic head and place in foil. Drizzle with 1 teaspoon of oil and close foil around garlic.
Line a baking sheet with parchment paper. Arrange tomatoes and onion in a single layer and drizzle with avocado oil. Sprinkle with salt and pepper.
Place garlic and tomato mixture in a preheated oven and cook for 25 to 30 minutes, until slightly shriveled.
Carefully open garlic and allow to cool. Gently press cloves from garlic head and place in a small bowl, breaking garlic into smaller pieces with the back of a fork.
Meanwhile, bring broth to a boil. Add lentils and reduce heat. Simmer, covered, for 25 to 30 minutes, or until tender. Drain and transfer to a bowl.
Add garlic, tomatoes, red onion, celery, red pepper to the bowl.
Make dressing by combining olive oil, lemon juice, and crushed pepper in a small bowl. Whisk in salt and paper to taste. Toss with lentil mixture and serve.