Preheat your oven to 225C with the grill/top heat on. Cover a baking tray with tinfoil and brush with olive oil. Cube the sweet potato, arrange on the tray and brush the tops with olive oil. Put into the oven and roast for around 15 minutes until slightly charred, turning them once. Take the potato cubes out, put into a bowl to cool and set aside. Half the pepper length-wise and clean. Put skin side up onto the tray and brush with olive oil. Roast until the skin is charred, around 7 minutes. Once done, take the peppers out of the oven and leave to cool.
Cook the lentils and quinoa (separately) according to packet instructions – this might vary from brand to brand, but will take around 15 minutes. Boil the eggs for 8 minutes. Cut the roasted peppers into strips. Once the quinoa and lentils are cooled, you can start to assemble your bowl. Arrange the potato cubes, lentils and quinoa in the bowl.
Cut the tomatoes into halves and slice the avocado. Arrange the pepper strips, tomatoes and avocado on top of the first layer. Add the cubed feta cheese, sliced olives, halved eggs and basil leaves. Drizzle the lemon juice and olive oil all over and add a little pepper to taste.