On a parchment-lined baking sheet, toss the cauliflower with 1 tablespoon of olive oil, 1/2 teaspoon ground cumin and 1/2 teaspoon salt. On a second parchment-lines sheet pan, toss the sweet potatoes with 1 tablespoon olive oil, 1/2 teaspoon ground cumin and 1/2 teaspoon salt. Transfer the pans to the oven and roast until the veggies are lightly browned and caramelized, about 30 minutes, switching the pans from top to bottom halfway through.
Transfer half the sweet potatoes and all the cauliflower to a food processor or blender and pulse until a coarse paste forms, with still a few chunks of cauli. Set aside in a large mixing bowl, along with the remaining sweet potatoes, almond flour, egg, chili powder, cilantro and lime zest. Fold the mixture together until well-incorporated.
Form the mixture into 5 or 6 thick 3-inch patties and set aside on a plate. The mixture will be rather sticky. Refrigerate for 20 minutes uncovered, until the burger mixture is cool and firm.
Meanwhile, make the condiments: in a small mixing bowl, mash the avocado with the lime juice and a generous pinch of salt until coarsely combined.
Make you Sriracha Mayo by mixing all ingredients together.
Preheat the oven to 425 degrees F.
Heat a large non-stick skillet over a medium-high flame (see note). Add a thin layer of olive oil. Add the veggie burgers (3 at a time) and cook until the top has set, about 3 minutes. Flip the burgers and continue. These are going to feel very mushy at this stage, so if they’re misshapen after you add them to the pan, and/or after you flip, just use a silicon spatula to gently nudge the sides back into a round patty shape.
Transfer to a parchment lined baking sheet with the buns, cut-side up, and bake in the oven for 10 minutes.
While the burgers toast, prepare the sriracha mayo (if you haven’t premade).
Top each bun with a burger, followed by the avocado mash, mayo and sprouts. Serve alongside the remaining sauce.