Step 3 - Prepare Tuna Salad
For the tuna salad: mix drained tuna, mayonnaise (or dijionnaise - if you prefer a mustard flavor), onion, celery salt, paprika, sea salt, lemon juice and the remainder of the scooped-out avocado. Scoop the tuna salad mixture into the avocados. Without adding cheese, bake for 5 minutes to warm the tuna and avocado.
Slice provolone cheese while avocados are in the oven. Remove avocados and cover with cheese. Turn broiler on high. Return avocados to oven and warm for 1-2 minutes until cheese melts and bubbles - be careful not to burn. Remove when the cheese begins browning.