Combine the BERBERE SPICE ingredients together in a small bowl and set aside.
Melt the butter in a dutch oven or large pot over medium heat. When the butter is melted add the onion and 1/4 tsp salt. Cook the onions, stirring occasionally, until softened and browned, about 30 minutes.
Stir in the berbere spice mix, tomatoes, lemon juice, and water. Nestle the chicken thighs into the pot and bring to a boil over medium-high heat.
Cover the pot and reduce the heat to medium-low. Simmer over medium-low heat until chicken is tender, about 1 hour.
Add the eggs to a small saucepan and cover with warm water. Bring to a boil over medium-high heat. When water begins boiling place a lid on the pan and turn off the heat. Let eggs sit while covered for 10 minutes. After 10 minutes drain the eggs and rinse under cold water then carefully peel the eggs and set aside.
Transfer the chicken from the pot to a cutting board and use two forks pull the chicken from the bone. Discard the skin and bone and stir the chicken back into the pot.
Continue to simmer the stew over medium-low heat, uncovered, until the stew thickens, about 20 minutes. Season with additional salt & pepper to taste.
Take the stew off the heat and stir in the whole hard-boiled eggs. Serve the stew with flatbread.