In a large skillet, add the kale and ½ cup water. Cover with a lid and simmer over medium heat for 3 minutes or until the kale has wilted down.
Transfer the kale and liquid to the blender (scrape out every last bit!) along with the pumpkin seeds and remaining ½ cup water. Blend until smooth, making sure to allow steam to escape, about 1 minute.
In the same skillet over medium-low heat, add the olive oil, garlic, and red pepper flakes (if using). Once the garlic starts to sizzle, cook for 1-2 minutes or until garlic is fragrant, stirring often.
Stir in the beans and ½ teaspoon salt and cook for 30 seconds, stirring often. Turn off the heat and stir in the kale sauce. If the sauce looks too thick, add another ¼ cup water. You want the sauce to be more water-y than thick (it will thicken as it simmers).
Season fish on one side with about ¼ teaspoon salt, then nestle it into the liquid (salted-side-down) so it’s mostly or totally submerged. Season the tops with another ¼ teaspoon salt (don’t worry if the tops are submerged, just sprinkle the salt on top).
Cover with a lid, turn the heat to high to bring it to a rapid simmer, then reduce the heat to low or medium-low and simmer for 8-10 minutes or until the fish flakes easily with a fork. Give the pan a gentle shake halfway through. If using very thick fish, flip it halfway through the cook time. If your fish is very thin, it might take as little as 6 minutes to cook through, so use your judgement! You can always continue to simmer and add more water, if needed.
Turn off the heat and transfer the fish to a plate. Stir the parm into the skillet.
To serve, scoop the beans/kale sauce into your bowl and top with fish. Sprinkle more parm over top along with some black pepper, a drizzle of good olive oil, and a generous squeeze of lemon.