In a mixing bowl, combine the soy sauce, lemon juice, salt, honey, and bagel seasoning and whisk to combine.
Put the 2 tuna steaks in a dish and pour marinade over the tuna.
Let this refrigerate for 1 hour up to 5 hours.
Remove the marinated tuna from the fridge
In a cast iron skillet or dutch oven, melt the coconut oil over high heat.
Sear the tuna steaks 1 at a time for 30 seconds on each side.
Repeat with the 2nd tuna steak.
Set on a cutting board and let them rest for 5 minutes.
Slice against the grain of the tuna into 1/4 inch slices, then cut again to create cubes.
In a mixing bowl mix together the salad mix (usually these salads come with dressing and crunchy toppings, add it all in!)
Fill each taco shell with some salad and top with tuna cubes and sliced avocado.