Sea Bass and Tomato Ceviche

Name: Sea Bass and Tomato Ceviche
Ingredients: 1/4 medium red onion, chopped, plus thin slices for serving; 1 large celery stalk, chopped; 2 garlic cloves, smashed; 1/4 habanero chile, seeded; 1 tablespoon chopped peeled ginger; 1/2 teaspoon sugar; 1 tablespoon kosher salt, plus more; 1/3 cup coarsely chopped fresh cilantro; 1 pound sea bass fillet, skin, bones, and bloodline removed; 1/2 cup passion fruit juice or fresh orange juice, strained; 1/2 cup (or more) fresh lime juice, strained; 1 pound mixed heirloom tomatoes, whole or cut into wedges, depending on size Microgreens (for serving)