Combine red onion, vinegar, sugar and ½ teaspoon salt in a small bowl. Let sit at room temperature at least 30 minutes, or up to 2 days in advance, in the refrigerator. Drain before using.
In a medium pot, combine quinoa, a large pinch of salt and 1 cup water. Bring to a boil over high heat. Top with a lid and reduce heat to low. Cook 12 minutes. Remove lid and continue to cook, stirring occasionally and adjusting heat if necessary, until water is evaporated and quinoa is tender but still al dente, about 4 minutes more.
Preheat a large nonstick skillet over high heat. Add 3 tablespoons olive oil and swirl to coat. Add tortilla strips, season with salt, and saute, stirring frequently until deeply golden brown, about 4 minutes. Remove to a paper towel-lined plate to drain.
Season fish with salt and pepper. Wipe out skillet and add remaining 1 tablespoon olive oil. Add fish and press down on fillets with the back of a spatula to encourage crisping and prevent the fish from curling. Cook until golden on the underside, about 2 minutes. Flip and continue cooking until fish is just cooked through, about 2 minutes more. Remove to a plate and squeeze lime halves over fillets.
Divide cabbage, kale, avocado, pickled red onions, tortilla strips, fish and quinoa among serving bowls. Top with cilantro leaves and queso fresco dressing and serve.
For the Queso Fresco Dressing:
In a blender, combine olive oil, lime juice, yogurt, queso fresco, cilantro, garlic and jalapeno. Blend until smooth. Season to taste with salt and pepper. Alternatively, you can use an immersion blender and place ingredients in a glass measuring cup. Leftover dressing will keep in the refrigerator for 1 week.