Season the tuna with salt and pepper. I use smoked salt and smoked pepper for extra flavor
Slice the tuna against the grain into thin strips, about a quarter inch thick
Measure out the sour cream in a small prep bowl
Zest the lime and add zest to the prep bowl.
Cut the lime in half and extract the juice. It helps to roll the lime on the counter with the palm of your hand. You might need two limes to obtain 2TBSP of juice. I've seen TV chefs just squeeze lemons and limes with their fists to extract juice, but this never works for me. I have a simple, plastic juicer that does a great job of extracting all the juice.
Mash about 1/2 small avocado into prep bowl (if using)
Put the diced onion and minced garlic and ginger into the prep bowl
Put the chopped cilantro into the prep bowl
Lightly season with salt and pepper to taste. I don't measure, but instead use a few twists of my salt and pepper mill. Add sweetener if using.
Mix the ingredients together and let sit for at least five minutes. If you prepare ahead of time, store covered in the refrigerator for up to four days.
Dust with sesame seeds (optional) I used "tuxedo" seeds, a mix of regular and black sesame seeds.
