Dip the flounder in the egg until coated. Transfer to the bread crumb and coat.
Dip the flounder into the egg once more and then again transfer to the bread crumb and coat.
Heat up the light olive oil in the cast iron skillet
Place the fillets in the oil once heated up and let it cook about 4-5 minutes before flipping and then cooking the other side another 4-5 minutes.
Once done, remove the fillets from the pan onto a plate covered with paper towels to drain some of the oil.
In a wide mouth mason jar, add olive oil, egg, dijon mustard, lemon juice, and salt.
Using an immersion blender, blend the mayonnaise. Start at the bottom and slowly move the immersion blender up and down while it is blending until the mayonnaise becomes thick.
Once done, add the sweet relish and mix with a spoon.
Top the flounder with tartar sauce before serving.