Preheat the oven to 400°F. Add the quinoa, ¾ cup water, and a pinch of salt to a small saucepan over high heat. Bring to a boil, cover, and reduce heat to low. Cook until all the water is absorbed and the grains begin to burst, about 12 to 15 minutes.
In a small bowl, mix together the flaxseed meal with 1 tbsp warm water. Halve the lemon. In another small bowl, combine 1 tsp lemon juice, the Vegenaise, and the cajun seasoning. Season the cajun aioli with a pinch of salt and stir to combine. Trim the green beans.
Add the oat flour, cornmeal, baking powder, and ¼ tsp salt to a large bowl. Measure out ½ cup almond milk (reserve the rest for your own use) and add to the large bowl. Add the flaxseed mixture and whisk the batter until there are no lumps. Stir in the green peas and corn.
Add the green beans to a baking sheet. Toss with 2 tsp olive oil and a pinch of salt and pepper. Roast until just tender and lightly browned, about 8 to 10 minutes.
Place a large nonstick skillet over medium heat and add ¼ cup vegetable oil. Once hot, use the ¼ cup measuring tool to drop the batter into the hot oil, then flatten slightly to form a ½ inch thick cake (you should get 6). Cook until lightly browned, about 5 minutes per side. Transfer the cakes to a paper towel-lined plate and immediately sprinkle with salt.
Cut the remaining lemon half into wedges. Divide the cooked quinoa and roasted green beans between plates. Top with the sweet pea corn cakes and drizzle with the cajun aioli. Serve with lemon wedges.