In a large pot or Dutch oven, melt the butter over low heat.
Add the finely chopped tomatoes and curry powder.
Cook for 3-4 minutes, using the back of a spoon to gently crush the tomatoes and release their juices, creating a fragrant paste.
Pour in the unsweetened coconut milk and chicken broth.
Stir everything together and bring the mixture to a gentle simmer for 4-5 minutes.
Add the cubed beef to the pot, stirring to coat. Increase the heat to medium and bring the curry to a boil.
Once boiling, reduce the heat to the lowest setting, cover the pot, and let it simmer for 2. 5 hours.
Stir occasionally to prevent sticking.
After 2. 5 hours, the beef should be tender. Use a slotted spoon to carefully transfer the beef to a separate bowl and set aside.
Allow the curry sauce in the pot to rest off the heat for about 10 minutes. This will allow the fat to rise to the surface.
Skim the excess fat from the top of the sauce with a spoon and discard.
Return the pot to medium heat.
Add the cooked beef back into the sauce and bring it to a gentle simmer.
Continue to cook, uncovered, for about 30 minutes, or until the sauce has thickened to your desired consistency.
Season generously with salt and freshly ground black pepper to taste.
Remove from the heat.
Garnish with a generous sprinkle of fresh, chopped cilantro and serve immediately.
Sear the Beef First: For an incredible depth of flavor, pat the beef cubes dry and sear them in a hot, oiled pan until browned on all sides before adding them to the sauce. This caramelization makes a world of difference!