Sea Bass and Tomato Ceviche

Purée chopped onion, celery, garlic, habanero, ginger, sugar, 1 tablespoon salt, and 1/4 cup water in a blender until smooth. Transfer to a small bowl; stir in cilantro. Cover and chill 1 hour. Meanwhile, trim fish to create clean edges. Holding your knife at a 45 ° angle, slice into 1/4"-thick pieces; try for one fluid movement per slice to avoid shredding flesh. Transfer to a plate as you go, separating layers with sheets of plastic wrap as needed. Chill until ready to serve. Strain purée through a fine-mesh sieve into a small bowl, pressing down on solids to extract as much liquid as possible (you should have about 1/2 cup; this is your "leche de tigre"). Stir in passion fruit juice and lime juice, adding a bit more lime juice to balance acidity if needed. Arrange fish and tomatoes in shallow bowls; spoon leche de tigre over. Season with salt and top with sliced onion and microgreens. Serve immediately.