Make the berbere spice mix: Sift all the spices into a bowl and mix well. Set aside.
Place the red and yellow onions, garlic, and ginger into a food processor. Process for about 3 to 5 minutes until combined into a fine paste.
Place a medium pot over medium heat and add the oil. Once the oil is hot, add the onion, garlic, and ginger paste and saute, stirring occasionally, for about 10 to 15 minutes or until the mixture has softened, reduced, and become light brown.
Reduce the heat to medium low and add the tomato paste, 1 cup of water, berbere spice, and salt. Cook for 15 minutes more, stirring occasionally, until the tomato paste starts to darken.
Add the lentils and 4 more cups of water into the pot. Stir well and increase the heat to high, bring the pot to a boil, stirring occasionally. Then, place a lid on the pot and reduce the heat to low. Continue cooking the stew on a gentle simmer, for about 35 to 40 minutes, stirring occasionally, until the lentils are soft and cooked through.
Serve the stew hot with a side of dabo.