Wrap the sauerkraut in a clean kitchen towel and squeeze out as much moisture as possible.
Transfer the sauerkraut to a bowl and fold in tuna, shallot, and scallion.
In a separate bowl, whisk together tahini, sesame oil, and Dijon mustard until smooth. Add avocado and lemon juice, mashing or whisking until the mixture reaches the consistency of extra-thick mayonnaise.
Fold the avocado-tahini “mayo” into the tuna-sauerkraut mixture. Taste and adjust salt as needed.
Serve on lectin-free bread or crackers, in lettuce or endive leaves, or alongside a green salad.