Cut the corn from the cob and put into a bowl. Use the back of the knife and press to release the milk of the cob into the bowl with the corn.
Heat the butter in a large saute pan over medium heat. Add the onions and cook until soft, about 4 minutes. Add the garlic and cook for 30 seconds. Add the corn and corn milk to the pan.
Add the sugar and cook, stirring occasionally, until the corn begins to soften slightly and heats through, about 5 minutes. Add the edamame and tomatoes and cook for 2 minutes. Add the cotija and creme fraiche and season with salt and pepper. Cook for 1 minute longer.
Remove from the heat and stir in the lime zest, green onions and chopped cilantro. Transfer to a serving bowl and garnish with whole cilantro leaves.