Gently toss cornbread cubes in the melted butter and spread on a baking sheet. Transfer the sheet to the oven and bake for 5 minutes, shake the pan to turn the cubes a bit, then continue to bake for 5 to 10 minutes more or until the cubes begin to brown around the edges and turn crisp. Let cool on a wire rack.
dressing and salad
Set the oven to 400 degrees and line a rimmed baking sheet with parchment paper.
Spread the lemon slices on the baking sheet and lightly brush with olive oil. Place in the oven and roast for 10 minutes, remove the baking sheet, carefully flip the slices, brush with remaining oil, and continue to roast for another 10 minutes or until the slices begin to brown along the edges and the juice caramelizes on the parchment paper beneath. Let the slices cool slightly, then cut into strips, wedges, or halves.
In a large bowl, toss together the kale, roasted lemon, and half the dressing. Taste and add more dressing if desired. Serve with additional parmesan and the cornbread croutons.