In a small bowl, combine the chopped parsley, minced garlic, lemon zest, and lemon juice to create the gremolata.
Pat the sardines dry with a paper towel and season both sides with sea salt and black pepper.
Heat the olive oil in a non-stick skillet over medium-high heat until shimmering.
Place the sardines in the skillet, skin-side down, and sear for 2-3 minutes until the skin is golden and crisp.
Carefully flip the sardines and cook for an additional 1 minute until the flesh is opaque and tender.
Rinse the cannellini beans and warm them briefly in a small pan with a tablespoon of water until heated through.
Layer the baby arugula on a plate, top with the warm beans, and arrange the sardines over the beans.
Finish the dish by spooning the fresh gremolata over the sardines for a burst of citrus flavor.