In a shallow bowl, combine flour, salt, and pepper. Set aside.
Flake tuna and gently combine with Pesto Mashed Potatoes. Alternately, you could use 1 1/2 cups plain mashed potatoes with 1/4 cup pesto.
Gently form mixture into 16 patties. Lightly press into the flour mixture on each side, shaking off excess.
Heat about a 1/4 inch of canola oil in a cast iron pan over medium heat. Fry tuna cakes in batches. Cook on both sides for about 3-4 minutes or until golden brown. Serve warm.