Melt the coconut oil in a large pot over medium heat, and saute the onions until they are tender and golden, about 10 minutes. Add in the minced garlic and saute until fragrant, about 1 minute. Add in the carrots, beet, and water and bring the mixture to a boil. Cover and lower the heat to a simmer, cooking until the carrots and beets are fork-tender, about 30 to 40 minutes.
Carefully transfer the mixture to a high-speed blender, add the salt and lemon juice, and blend until smooth. (Be sure to cover the vent in the lid of your blender with a dishtowel to prevent the top blowing off from the pressure of blending hot liquids!) Taste the sauce and adjust any seasonings, as needed, including a dash of oregano and basil, if you like! You can also add additional water, if you'd like a thinner sauce.
Serve warm over your favorite vegetable or pasta dish, and enjoy! Leftover sauce can be stored in a sealed container in the fridge for up to a week, or in the freezer for months.