Peel and cut carrots on the diagonal, into pieces 1/2 inch thick and 3 inches long.
Place carrots on a parchment paper-lined baking sheet. Add 2 Tbsp. olive oil and 1/2 tsp. of salt. Toss until the carrots are lightly coated in oil and salt. Arrange them in a single layer.
Roast in a 400° oven for 25-40 minutes or until they are easily pierced with a fork, tossing halfway through. Add the onion, 1 Tbsp. olive oil and the other 1/2 tsp. salt to the baking sheet for the last 5 minutes of cooking.
When the carrots and onions have cooled somewhat, place the carrots, onions, garlic, seasonings, and 4 cups of vegetable broth or water in a large resealable bag. Remove excess air and seal. Freeze.
Cooking instructions:
Thaw. Pour bag contents into a large pot. Add 2 cups of water and bring to a boil over high heat, then reduce to a simmer for 15 minutes.
Remove from the stove and allow to cool a bit. Blend with an immersion blender until well blended. Add lemon juice and pepper. Serve.