Preheat the oven to 425º F. With a sharp knife, slice the pork butt into 4 to 5 steaks that are roughly the same size, about 6 to 8 ounces each. Don’t worry about them being perfect or evenly sliced; they should just be similarly sized. Season them with salt, pepper and the fennel seeds. Set aside.
Make the white bean salad by slicing the radishes thinly and adding to a large bowl with the white beans. Squeeze the halved lemons into the bowl, toss in the 1 tablespoon oregano, anchovy and garlic. Season with salt then pour the olive oil over. Set aside.
Heat the canola oil in a large (12-inch diameter) skillet over high heat. Once hot, carefully place the pork steaks in, pressing them down firmly with tongs. Sear and cook like so, undisturbed, until a golden brown crust has formed, about 6 minutes. Turn the steaks over, arrange the lemon slices in between, turn off the heat and transfer the skillet to the oven. Roast the steaks until cooked through (145º F with an instant read thermometer stuck into the middle of thickest piece). Turn off the oven and transfer steaks to serving plates.
Carefully (the handle will be hot!) bring the skillet back over medium heat on the stovetop. Sizzle the lemon slices, turning and tossing them frequently until browned and caramelized, then add to the bowl with the beans.
Toss the arugula into the bean salad, spoon salad over the pork steaks and serve immediately.