Pat the lamb pieces dry with paper towels. Season evenly with 1 tsp kosher salt, 1/2 tsp freshly ground black pepper and 1 tablespoon of the berbere spice. Toss to coat and let sit at room temperature for 15 minutes while you prep the other ingredients.

Sear the lamb

Heat a large heavy-bottomed skillet or cast-iron pan over medium-high heat. Add 2 tablespoons neutral oil and 1 tablespoon unsalted butter. When the fat is shimmering and butter foaming, add the lamb in a single layer (work in batches if needed so meat sears rather than steams). Sear 2–3 minutes per side until well browned. Remove lamb to a plate and set aside, leaving the fond (browned bits) in the pan.

Cook the aromatics

Reduce heat to medium. Add the sliced onion to the pan and a pinch of salt. Cook, stirring occasionally, 5–7 minutes until softened and beginning to brown. Add the minced garlic and sliced jalapeño and cook 1–2 minutes until fragrant, taking care not to burn the garlic.

Build the sauce

Stir in 1 tablespoon tomato paste and cook 1 minute to remove raw flavor. Add the diced tomatoes (or canned crushed tomatoes) and 1/2 cup beef or lamb stock, scraping up browned bits from the pan. Add remaining 1/2 tablespoon berbere, 1 tsp smoked paprika, 1/2 tsp chopped rosemary and 1/2 tsp thyme. Bring to a gentle simmer.

Finish cooking the lamb

Return the seared lamb and any accumulated juices to the pan. Stir to combine, cover partially, and simmer over medium-low heat 12–15 minutes, stirring once halfway through, until the lamb reaches medium-well (internal texture should be mostly cooked through but still tender). If the liquid reduces too quickly, add up to 2–4 tablespoons more stock or water to maintain a glossy sauce.

Adjust seasoning and reduce

Uncover and increase heat to medium to reduce the sauce for 2–3 minutes until slightly thickened. Taste and adjust seasoning: add up to 1/2 tsp more berbere or mitmita if you want extra heat, and more salt if needed. Stir in 1 teaspoon fresh lemon juice to brighten.

Garnish and serve

Remove from heat and garnish with 2 tablespoons chopped cilantro or parsley. Serve immediately with injera, steamed rice, or flatbread. Leftovers will keep chilled for up to 3 days.