Pat 3 pounds of cubed chuck roast dry with paper towels, then season generously with salt and pepper on all sides.
Heat a large skillet over medium-high heat. Add 1 tablespoon of avocado oil and once hot, sear the beef in small batches until browned on all sides, adding more oil between batches as needed. Avoid overcrowding the pan to ensure proper browning.
Transfer the seasoned beef to the pan of your slow cooker as each batch is finished.
Add the diced onion, minced garlic, and minced ginger on top of the seared beef in the slow cooker.
Pour in the can of diced tomatoes and the can of coconut milk. Add the cornstarch slurry (3 tablespoons cornstarch mixed with 3 tablespoons water).
Add the red curry paste, ground cumin, garam masala, and cayenne pepper. Stir all ingredients until well combined.
Cover with the slow cooker lid and cook on LOW for 6-8 hours or on HIGH for 4-6 hours, until the beef is tender and falls apart easily when pierced with a fork.
Before serving, stir the curry and taste. Adjust seasonings if needed, adding more salt, pepper, or spices to taste.
Garnish with fresh chopped cilantro and serve over white rice with naan bread on the side.
Notes
Take the time to properly sear the beef in batches for the best flavor. This crucial step creates the Maillard reaction, which adds depth and richness to the final dish.
If you're short on time in the morning, prep the ingredients the night before. Cut the beef, chop the aromatics, and mix the spices so everything is ready to go.
For the most tender results, cook on LOW rather than HIGH. The longer, slower cooking time allows the connective tissue in the beef to break down more completely.
If your curry sauce is too thin at the end of cooking, remove the lid for the last 30 minutes to allow some liquid to evaporate, or use the cornstarch slurry to thicken the curry.
For deeper flavor, toast the cumin and garam masala in a dry pan for 30 seconds before adding them to the slow cooker. This wakes up the essential oils in the spices.
Stir the curry occasionally if cooking on HIGH to prevent the edges from burning, especially if your slow cooker runs hot.