Melt 3 tablespoons of the butter in a 10-inch straight-sided saute pan over medium-high heat. Add the butternut squash and a large pinch of salt. Cook, stirring occasionally at first and then more frequently as the squash browns, until the squash is tender and lightly browned, about 15 minutes. Push the squash to one side of the pan and add the remaining tablespoon of butter to the clear space. When the butter melts, add the ginger, garlic, and 1/2 teaspoon salt. Cook the aromatics in the melted butter, stirring constantly and scraping the bottom of the pan until they are softened, 1 to 2 minutes. Stir the cumin, coriander, cinnamon, and cayenne into the ginger and garlic and cook until fragrant, about 30 seconds. Stir the flavorings into the squash, adjust the salt to taste before serving, and garnish with the cilantro, if using.