Homemade Whitefish Salad

• 3/4 cup good-quality mayonnaise
• 1/2 teaspoon finely grated lemon zest
• 2 tablespoons freshly squeezed lemon juice
• 2 pounds smoked whitefish, skinned, boned and flaked
• 1 large stalk celery, finely diced
• 1/2 small red onion, finely diced
• Kosher salt and freshly ground black pepper
• Bagels, for serving
• Pickled Red Onions, for serving, recipe follows

Pickled Red Onions:

• 1 cup red wine vinegar
• 1/4 cup fresh lime juice
• 3 tablespoons granulated sugar
• 1 tablespoon kosher salt
• 1/4 teaspoon coriander seeds
• 1/4 teaspoon mustard seeds
• 1/4 teaspoon black peppercorns
• 1 medium red onion, halved and thinly sliced