Combine all ingredients in a medium bowl. Cover and refrigerate 2 hours or overnight.
While the gravy simmers, skewer meat and fully cook on a grill or in a hot oven (see Notes for instructions on how to cook it in the oven).
For the Gravy:
Heat the ghee over medium heat in a large, deep-sided pan with a lid. Once hot, add the onion, bell pepper, salt, and black pepper, and sauté (uncovered) until starting to soften but not brown, about 5 to 7 minutes, stirring occasionally.
Add the jalapeno, garlic, and ginger, and sauté 1 minute, stirring constantly.
Add the bay leaf, 2 ½ teaspoons garam masala, coriander, cumin, and crushed red pepper flakes, cinnamon, cardamom, cloves, nutmeg, and fenugreek, and sauté until fragrant, about 30 seconds, stirring constantly.
Stir in the broth, tomato sauce, tomato paste, sugar, and lemon juice.
Bring up to a boil, cover the pan, turn heat down to low, and simmer until the vegetables are tender and the sauce is thickened, 20 to 30 minutes, stirring occasionally.
Turn the heat off and stir in remaining ½ teaspoon garam masala, cream, cilantro, and cooked lamb. Taste and adjust seasonings as desired.
To Serve:
Serve the lamb tikka masala topped with a sprinkle of fresh chopped cilantro if desired, alongside prepared basmati rice.
Notes
Storage: Store leftovers covered in the fridge for up to 4 days or in the freezer for up to 3 months.
Reheating: Cook over medium-low heat on the stovetop until warm throughout, making sure it doesn’t come to a boil (to prevent cream from curdling).
Meat Options: Instead of lamb, sometimes I also make this dish with chicken, beef, or bison. If you make it with chicken, use chicken broth instead of beef broth; the other ingredients and cooking methods are the same.
To Cook the Meat in the Oven: If you have large metal skewers, skewer the meat and place it so meat is suspended and the metal skewers hang over the sides. If you don’t have large metal skewers, place the meat on a foil-lined baking tray. Cook the meat in a 500F oven for 15 minutes, and then broil it for 5 minutes (flipping halfway through broiling) to brown it.