Add red onions, oil, and salt to a saucepan and set it on the lowest temperature.
Keep it on low, and stir occasionally. Cook until the onions are sticky, transparent and caramelized. This process will take approximately 40 minutes. Don’t be tempted to turn up the heat; this process needs to done low and slow. Set aside.
Heat a cast iron, or heavy pan to a high heat. Prepare the schnitzel by seasoning it liberally with salt and pepper. Drizzle the meat with oil, and cook in the hot pan, turn once well browned (this should take 40 seconds -1 minute), and repeat on the second side. Remove from the pan immediately after cooking.
Drizzle 1 TB olive oil on a chopping board, and finely grate in the clove of garlic. Rest the meat in the garlic oil, turning it to coat.
Cut the bread into desired size for your sandwich. I like to cut a wide piece and then slice in half horizontally. Warm in low oven, or toast if desired.
Build the sandwich starting with a generous layer of Kasundi, followed by the spinach, then the schnitzel, onions, and butter the top piece of bread.