Mix together the grated squashes, tarragon, lemon juice and zest, and egg in a medium bowl. Stir in the cornmeal, flour, and salt until just combined.
Meanwhile heat a thin layer of vegetable oil in a large cast iron skillet over a medium-high flame. When the oil is hot, add the batter in tablespoon-fuls to the pan, making sure not to crowd the cakes. You should be able to fry about 8 at a time, depending on the size of your pan. Press each mound of zucchini down with the back of your spatula to form flat little patties, about 2-inches in diameter. Cook until golden brown on the first side, about 1 to 2 minutes, and then flip and cook until crispy on the second side.
Remove the cooked cakes to a paper towel to drain. Add more oil as necessary, and repeat with the remaining batter.
Serve the cakes with a dollop of aioli and garnish with some fresh herbs, lettuce, or pickled veg - radishes worked great!