Add 1 cup of amaranth to a pot with 2½ cups of water. Bring this to a boil, then cover and reduce heat to low. Let the amaranth cook for about 20 minutes or so until all the liquid is absorbed. Once it's done you'll see it has a really thick porridge-like consistency.
Meanwhile, chop tomatoes, onion and avocado. Toss in a bowl with pumpkin seeds, sunflower seeds, salt and a small drizzle of olive oil. Add oregano now if desired.
Pour amaranth porridge into two bowls and top each with half the chopped tomatoes, onion and avocado mix.
You can save the second bowl of cooked amaranth for tomorrow morning, simply reheat and add toppings then.