Toss the pumpkin seeds, sunflower seeds and puffed rice with the cumin, chili powder, garlic powder and kosher salt in a bowl. Add the oil and toss to coat. Place on a baking sheet in a single layer and bake until toasted, about 10 minutes. Toss with the lime zest and set aside.
Cut the avocados in half and peel. Place the flat side of each avocado on a cutting board and slice at an angle. Plate half an avocado on each plate and top with some of the Pickled Onions and toasted seed mixture. Finish with a drizzle of good-quality olive oil, a sprinkle of cotija and a pinch of flaky salt. Serve with a lime wedge.
Combine the apple cider vinegar, sugar, salt and 1/4 cup water in a small pot. Heat, stirring, until the sugar and salt are dissolved. Pour the mixture over the red onions in a medium bowl and let sit for about 10 minutes.