Preheat oven to 200 °C (400 °F). Transfer onion, tomatoes and jalapeño on a baking sheet. Drizzle with olive oil and bake in the oven for 25 minutes or until golden brown. Set aside.
Using a food processor or blender, roughly purée the roasted vegetables with the juice from the pan. Season with salt and pepper. Transfer into a bowl and add corn, cilantro and zest and juice of the lime.
For the tempeh, in a bowl, mix all the ingredients. In a large pan, heat oil and cook the tempeh until golden brown.
For the avocado cream, using a food processor or blender, purée all the ingredients until smooth and season with salt and pepper.
In a pan, heat oil and fry the tortillas. Transfer to a tray lined with paper towel to remove excess oil.
Spread the avocado cream on the tortillas and top with tempeh and salsa.