In a food processor, whizz up the peeled beetroot roughly.
Add all the rest of the ingredients and whizz up again until you have a burger-ish kind of mass. NB Don't over process! You want some texture.
Refrigerate the burger mixture patties for an hour to allow it to furm up a little
Add some oil to a non-stick fryiing pan and bring to a medium-heat
Scoop out the burger patties using a cookie scoop (or large spoon). Flatten with a spatula.
Allow the burger to fully cook on one side. Once it forms a 'crust' it will easily slip around in the pan, then you can flip it over and cook through on the other side (about 5 mins each side)
You need to form a 'crust' before flipping the burger to help these hold together, so be patient while the burgers get a little bit of a crust. Use a thin slice to flip the burgers. Alternatively oven baking works really well too. (Bake at 180℃/360℉ for around 15 minutes or until crispy)
Serve on a bun with ALL the burger things you love.
Notes
If you don't have a food processor, grate the beetroot.. Use washing up gloves to avoid staining your hands! Mince the onion really finely, then use a potato masher or fork to mash up the lentils to create the burger.