Heat olive oil in a small pot with a well fitting lid over medium heat. Once hot, add the onion and cook until softened, about 3-4 minutes. Add the quinoa to the pot and toast the dry grains until most of them are golden brown. Add salt and pepper. Stir to avoid burning. When they nutty smell of quinoa fills the kitchen, add the tomato paste and stir until the grains are evenly coated. You want to be hearing a frying-sizzle sound which means the tomato paste is also getting nice and toasty. Add water and stir. Reduce heat to low, cover with the lid, and cook for 15 minutes. Remove from heat and steam in the pot with the lid of for an additional 5 minutes. Fluff with a fork and serve. Garnish with mint, cilantro, green onions or parsley if you have some on hand.