Step 1: Heat ghee or oil in a heavy skillet. Add onions and sprinkle with salt. Cook, stirring, until the onions are a deep golden brown.
Step 2: Add garlic, chili flakes, garlic, cumin and mustard and continue cooking until the onions are deep reddish brown, the garlic is golden and the mustard seeds pop.
Step 3: Add the broccoli rabe and stir to coat with the ghee or oil and then after it wilts slightly, add the lemon juice, and continue cooking, stirring, until the leaves wilt and turn a deep green.
Step 4: Add salt to taste and serve immediately.