Begin by rinsing and finely dicing the onion, garlic, eggplant, and red bell pepper. In a small saucepan, combine the rolled oats with ½ cup of water and allow them to simmer over low heat for about 10 minutes, until soft and slightly thickened.

In a separate skillet set over medium heat, drizzle a little olive oil and sauté the garlic and onion until they begin to soften and turn fragrant. Add in the chopped eggplant and red bell pepper, stirring occasionally to ensure even cooking. Incorporate the tomato sauce, cooked oats, grated beetroot, and ground flaxseed. Season with salt as desired and cook the mixture for another 5 minutes, stirring well to combine all the ingredients.

Once cooked, transfer the entire mixture to a food processor or blender and pulse until it reaches a coarse, moldable texture—firm enough to shape but not overly smooth. Allow the mixture to cool slightly. Lightly grease your hands with olive oil and begin shaping the mixture into small balls. Flatten each into a patty shape, ensuring an even thickness for uniform cooking.

For the final step, you can either grill the patties in a hot skillet until they develop a light golden crust on both sides or bake them. To bake, brush each burger with olive oil and place them on a lined baking tray. Bake in a preheated oven at 200°C (392°F) for approximately 20 minutes, or until firm and lightly browned.