Preheat the oven to 375 degrees F (190 degrees C). Grease a 9x13-inch glass baking dish. Heat a large nonstick skillet over medium heat. Cook sweet potatoes, stirring occasionally, until soft, 10 to 15 minutes. Transfer to a large bowl. Add sausage to the skillet; cook and stir until browned and crumbly, about 10 minutes. Add onion, jalapeno, and garlic and cook 3 minutes more. Transfer mixture to the bowl with the sweet potatoes and add tomatoes. Stir and spread into the prepared baking dish. Whisk eggs, milk, cream, 1 1/2 cups Cheddar cheese, and salt together in a bowl. Pour over mixture in the baking dish. Sprinkle remaining Cheddar cheese on top. Bake in the preheated oven until top is golden brown and knife inserted in the center comes out clean, 30 to 45 minutes. Let stand 5 minutes before serving.