Heat 1/2 cup butter in a skillet over medium-low heat. Cook and stir onion until translucent, 5 to 6 minutes. Add 1/2 cup water and tomato paste; stir until hot, about 2 minutes. Stir in remaining butter, berbere, garlic, and ginger. Adjust heat to low and cook until mixture thickens to paste consistency, 20 to…