Preheat the oven to 350°F (180°C). Line a flat baking tray with kitchen baking paper.
Cut the tomatoes in half, and place them onto the baking tray. Quarter and deseed the bell pepper (capsicum), and place the pieces onto the tray. Bake for 1 hour or until the bell pepper is soft, turning the vegetables once during cooking. When the vegetables are ready, remove them from the oven. Place the bell pepper pieces into a plastic bag to cool (this will allow them to sweat a little, which makes it easier to remove the skin), before taking off the skin. Place the tomato and bell pepper flesh into a blender jug and mix until smooth.
Finely chop the onion and celery. Heat the olive oil in a large saucepan over medium heat, and add the onion, celery, and fennel seeds. Reduce the heat to low, and cook the mixture for 10 minutes, stirring occasionally. Add the pureed tomato and bell pepper, as well as the vegetable stock. Cover and bring the soup to the boil over medium-high heat. Add the quinoa and amaranth, and cook the soup for 40-50 minutes or until the grains are tender. If the soup begins to thicken too much, add extra water 4 fl oz/120 ml at a time. Season with salt and pepper to taste. Serve the soup topped with parsley as well as a drizzle of extra virgin olive oil.
Tip: To toast the fennel seeds, preheat a small frying pan over medium-high heat. Add the seeds, and cook for 2-3 minutes or until they are fragrant and lightly browned.