Put the crabmeat in a bowl and use your hands to pick the meat free of any shells. Do this at least twice.
In a medium bow, whisk the eggs until they're light and foamy and then whisk in the mayonnaise and mustard.
Use a wooden spoon to stir in the lemon juice, scallions, red onion, salt, black pepper, and cayenne.
Fold in the Panko and then gently fold in the crabmeat so it doesn't get broken up from too much mixing. The batter should be just thick enough to barely hold together when frying. Refrigerate for at least 1 hour to help it firm up further.
In a large, deep skillet or pot, heat 2 inces of canola oil to 350 F.
Using 2 medium-sized spoons, drop a few spoonfuls of the crab mixture at a time into the oil and fry until a nice golden brown color forms on the outside, 1 to 2 minutes.
Use a slotted spoon to transfer the beignets to a plate lined with paper towels. Repeat with the remaining batter, frying in batches so as not to crowd the pan.
You can keep the cooked beignets warm in a 200 F oven, if desired.