For the crab cakes: In a mixing bowl, mix all the ingredients except the crab until thoroughly mixed. Gently stir in the crab, being careful not to break up lumps. Place in the refrigerator to chill while you prepare the corn relish.
For the corn relish: Preheat a grill pan over medium-high heat. Grill the corn on all sides. Kernels should be mostly browned and lightly charred.
Next, cut the tomatoes and onion into small dice, and then toss them in a bowl with the parsley, garlic, seafood seasoning, and vinegar. Then, cut the kernels from the cobs, being careful not to include any cob or silk. Add to the bowl and stir. Finish with the mayo, stirring well. (Add more mayo to the mix if too loose. Relish should be thick and easy to spoon onto the crab cakes.)
Next, portion the crab mixture into bite-sized cakes. Pour the flour onto a plate. Place the cakes in the flour and toss to coat lightly. You do not want a thick layer of flour.
Heat a large saute pan over medium heat. Add 3 tablespoons butter. When the butter is melted, add the crab cakes and cook until golden brown on both sides, 4 to 5 minutes per side. Transfer the cakes to a paper towel to drain. Season with salt.
Cook the rest of the cakes in batches, adding more butter as needed. You can wipe out the pan between batches if there are overcooked bits.
Top each cake with corn relish and serve.