Preheat the oven to 425°.
To make the hummus, rinse the lentils in a fine-mesh sieve under cold water until the water runs clear. Shake them around and remove any debris you find. Transfer the lentils to a small saucepan with 1 1⁄2 cups of the water, cover, and bring to a simmer over medium-high heat. Reduce the heat to low and cook for 10–15 minutes, or until the red lentils are tender and the water has been absorbed.
Transfer the lentils to a food processor with the garlic and process for about 3 minutes, or until creamy and smooth. Scrape the sides of the food-processor bowl well, then add the tahini, salt, pepper, and cumin. Process for another 3 minutes until creamy and thick. Scrape the sides of the bowl one more time. With the machine running, slowly drizzle in the lemon juice, olive oil, and remaining 2 tbsp. water. Scrape the sides one last time, taste, and adjust the seasoning if needed. Pulse a couple more times, then transfer to a clean bowl. The hummus will be loose and creamy.
Toss the carrots, onion, olive oil, cumin, sumac (if using), salt, and pepper on a baking sheet. Bake for 20–25 minutes, until caramelized and tender. Sometimes when carrots are a bit tough, they take a while to bake and can easily burn on the outside while still being too firm on the inside. To avoid this, when the exteriors are caramelized, turn off the oven and leave the pan inside for another 15 minutes. The carrots will continue to cook at a lower temperature and have
a chance to soften without burning.
Place the pine nuts in a sauté pan over medium heat and toast, tossing frequently, until they begin to darken, about 3 minutes.
To serve, spoon 2 heaping tbsp. hummus on each plate and top with carrots and pine nuts. Drizzle some of the olive oil from the sheet pan over the top.