Begin by preparing all of your ingredients, and then cooking your beets. Place the diced beet pieces in a large pot and fill it with enough water to just cover them. Bring to a boil, then lower the heat and simmer until the beets are tender, which should take about 20-25 minutes from the point that the water starts to boil.
In the meantime, we'll be preparing all the other ingredients. First, chop your onion, and heat the olive oil in a skillet over medium heat. Add your finely chopped onion and sauté until it becomes translucent, about 5 minutes. Add the minced garlic and continue to cook for another minute or two until aromatic, and then take it off the heat and set aside.
Once the beets are cooked, drain them and transfer them to a high-powered blender. Add the sautéed onions and garlic, coconut milk (if using), vegetable broth, dried thyme and oregano, sumac (if using), and salt to the blender as well.
Purée the ingredients until the mixture reaches a smooth, sauce-like consistency. If the mixture is too thick, you can add a bit more broth to thin it out.
Taste and season with more salt, if desired, then transfer the sauce back to the pot and reheat on low, stirring occasionally, until it's warmed through. Serve the sauce over your choice of cooked pasta, and garnish with freshly chopped herbs for an added touch of extra flavor and color.