Cut the tempeh into three even triangles.
Fill a small saucepan with salted water, using approximately 18g (1 tbsp) of salt per 500ml (2 cups) of water. Bring to a boil, then add the tempeh and simmer for 15 minutes.
While the tempeh is boiling, whisk together the lemon juice, apple cider vinegar, miso paste, nutritional yeast, salt, and water in a bowl until well combined.
Once the tempeh has finished boiling, transfer it directly into the marinade, ensuring it is submerged. Cover and refrigerate overnight (or for at least 12 hours) to allow the flavors to infuse.
Preheat the oven to 75°C (170°F). Remove the tempeh from the marinade, place it on a lined baking tray, and bake for 2 hours, or until it is firm and slightly dry.
Let the tempeh cool completely before crumbing or grating. Store in an airtight container in the fridge for up to 1 week.
