Preheat oven to 375°F. Line large rimmed baking sheet with parchment paper. Place the whole peppers and tomatoes cut side up on sheet. Bake 20 min.

Add garlic and onion to baking sheet and drizzle with oil. Bake 40 min., turning peppers once, until peppers and tomatoes are very soft and onion is tender. Set aside to cool.

Peel peppers discarding seeds and white membrane. Peel tomatoes. Puree in food processor with onions. Squeeze in garlic pulp and puree all veggies until smooth.

Transfer veggies to sauce pan and stir in stock and sage. Heat soup until simmering. Add pepper to taste.