1/4 cup plus 2 tablespoons extra-virgin olive oil, plus more for drizzling
2 lemons, sliced 1/4-inch thick
Salt and freshly ground pepper
Two 5-ounce bags baby spinach
2 tablespoons plain dry bread crumbs
Four 6-ounce skinless, boneless chicken breast halves
1/4 cup all-purpose flour, for dusting
1/2 cup pitted green Sicilian or Spanish olives, sliced
2 tablespoons drained capers
1 cup chicken stock or low-sodium broth
3 tablespoons unsalted butter, cut into small dice
2 tablespoons chopped flat-leaf parsley
Preheat the oven to 375°. Line a baking sheet with parchment paper. Drizzle olive oil on the parchment, then arrange the lemon slices in a single layer. Drizzle the lemons lightly with oil and season with salt and pepper. Roast for about 20 minutes, until the lemons begin to brown around the edges.
Meanwhile, heat a large, deep skillet. Add the spinach and cook over high heat, tossing, until wilted, about 2 minutes. Transfer the spinach to a strainer; press out the liquid. Wipe out the skillet and heat 2 tablespoons of the oil in it. Add the bread crumbs and cook over moderate heat, stirring, until toasted, 2 minutes. Add the spinach, season with salt and pepper and cook for 1 minute.
In a deep medium skillet, heat the remaining 1/4 cup of oil. Season the chicken with salt and pepper and dust with the flour, shaking off the excess. Cook the chicken over high heat, turning once, until golden, about 6 minutes. Add the olives, capers and stock and bring to a boil. Cook over high heat until the stock is reduced by about two-thirds, about 5 minutes. Add the roasted lemons, butter and parsley, season with salt and pepper and simmer just until the chicken is cooked through, about 1 minute.
Transfer the chicken to plates and spoon the sauce on top. Serve the spinach on the side.