Start by cooking your sushi rice to the package instructions. You'll want this slightly cooled to serve.
Next, prep all your vegetables, mango, and garnishes, making assembling the bowl fun and easy.
If you didn't pickle your onions in advance, go ahead and do that now; by the time you're done assembling, they will be picked JUST enough.
Drain the liquid from your can of tuna, and add the tuna to a small mixing bowl. Try not to break up the beautiful chunks of tuna - add the mayo, gochujang, and soy sauce, and you are done!
Then assemble the bowl! Make it beautiful and have fun. I add some extra gochujang, but if you want a spicy mayo sauce, make a double batch above, pour half on the tuna, and save half for the finished bowl!