Heat the vegetable oil in a large pot over medium heat. Add the chopped onion and sauté until translucent (about 3-4 minutes).
Add the grated carrot and beets. Cook for 5-7 minutes, stirring occasionally, until the vegetables soften.
Stir in the diced tomato (or tomato paste), vinegar, and sugar. Cook for another 2-3 minutes, then remove from heat.