In a food processor fitted with a metal blade, combine the mayo ingredients and puree until smooth.
Prepare the grill for direct cooking over medium heat (350° to 450°F).
Cut a few shallow slashes in each hot dog, and then grill over direct medium heat, with the lid closed, until hot all the way to the center, 4 to 5 minutes, turning occasionally. During the last 30 seconds to 1 minute of grilling time, toast the buns, cut side down, over direct heat.
Generously spread the avocado mayo inside each bun (you will not need all of it). Then add a hot dog, sauerkraut, tomatoes, cilantro, and onion. Serve warm.