Preheat oven to 500º and remove pizza dough from fridge, if pre-made.

Lightly grease a cast-iron skillet with olive oil, and spread the ball of pizza dough across the bottom of the skillet in an even layer, until the outer edges are flush with the sides of the pan. Drizzle with olive oil and use your hands or a pastry brush to thoroughly coat all surfaces of dough.

In a large, non-reactive stainless steel frying pan, add sliced fennel and shallot, 3 tablespoons olive oil, 1 tablespoon balsamic vinegar, and half a teaspoon sea salt. Sauté over medium heat, stirring frequently, about 17 minutes, until the fennel and shallot are browning and beginning to caramelize. Remove from heat, and put half this mixture into a small food processor or blender with 1/3 cup feta cheese. Blend into a smooth feta-fennel-shallot whip. Spread this mixture on dough in an even layer, leaving an inch perimeter around the outer edge of the pizza. Reserve ¼ cup of the remaining, unwhipped caramelized fennel and shallot for use in the kale salad, and sprinkle the rest on the pizza dough. If the dough shrinks, keep spreading it out to the edges of the pan.

Place cast-iron skillet in oven and cook for about 12-13 minutes, until the crust is a perfect golden brown and patches are getting a bit darker. (Leave in longer if you want a more deeply browned, crisper pizza.) Remove from oven, use tongs to remove pizza from skillet, and top pizza with kale salad.

While the pizza is in the oven, make the kale salad. Massage the chopped kale leaves with 1 tablespoon olive oil until tender, about a minute. Add lemon juice, ¼ cup caramelized fennel and shallot, 1/3 cup very thinly sliced radishes, and a pinch of flaky sea salt. Toss to meld flavors, then add 1/3 cup crumbled feta.

Distribute evenly atop baked pizza, and finish with grated parmesan or pecorino, to taste. Serve immediately.