Set the EGG for indirect cooking with a convEGGtor at 375°F/191°C; add the cast iron skillet to the EGG to preheat.
Add the ground beef to the cast iron skillet and season with 1 tablespoon Big Green Egg Ancho Chili & Coffee Seasoning, chili powder, cumin and cayenne pepper. Cook until completely done and remove the skillet from the EGG.
Cut off the ends of the zucchinis and cut lengthwise in half. Using a spoon, scoop out the middle out of the zucchinis; season the inside of the four halves with the remaining tablespoon Ancho Chili & Coffee Seasoning. Spoon the ground beef into each of the halved zucchini shells, and top with the red onion, and cheese.
Place the stuffed zucchini on the EGG and bake for 25 minutes, or until the zucchini is tender and the cheese is melted. Serve with sour cream and hot sauce. Enjoy!