Make the aioli and begin marinating the tuna early in the day. Microwave the lemon
and lime in a small bowl to release the essential oils
and set aside just long enough to be able to handle. Meanwhile, through the feed tube of a running blender
, add 1 at a time, the egg yolks, dry mustard, salt, and white pepper
. By this time, the micro-waved lemon and lime should be cool enough to handle. Leaving the blender running, squeeze the juice from half of 1 lemon through the feed opening, then add the oil in a slow stream. Remove to a bowl and refrigerate.
Season the tuna steaks with salt and pepper, place them in a nonreactive container and squeeze the rest of the lemon and the lime over them. Cover and refrigerate for 2 hours.
Heat the grill or preheat the broiler in the oven. Brush the marinated tuna with 1 tablespoon or so of olive oil. Cook until browned, until fish
flakes with a fork, 3 to 6 minutes per side, and then let rest. Leave grill hot or oven on to toast bread.
Brush olive oil (about 1 tablespoon per half) on Italian bread and toast lightly, either on the grill
or under broiler.
Flake the tuna, place in a bowl with scallions and fennel
and fold in the aioli. Spoon tuna mixture onto the toasted Italian bread
a small amount of balsamic vinegar over, and top with Cheddar
. Heat briefly in the oven to melt
with fresh dill
. This is great served with fresh tomato
soup, if desired.