Everything Hash Brown Cake with Pickled Red Onions and Green Onion Creme Fraiche

Name: Everything Hash Brown Cake with Pickled Red Onions and Green Onion Creme Fraiche
Ingredients: 1/2 red onion, thinly sliced; 1/2 cup fresh lime juice; 1/2 cup white wine vinegar; 2 tablespoons granulated sugar; 1 teaspoon kosher salt; 1/2 cup creme fraiche; 2 green onions, dark green and pale green part, thinly sliced; Kosher salt and freshly ground black pepper; 2 large russet potatoes; 1/2 cup clarified butter; 1 clove garlic, smashed; 3/4 teaspoon poppy seeds; 3/4 teaspoon flaked sea salt; 3/4 teaspoon sesame seeds; Freshly ground black pepper; Parsley leaves