Unless you want to roast your beetroot or spend hours boiling it, the quickest and easiest way to cook beetroot (and keep all the goodness and juice) is to microwave it. Trim off most of the leaves (leaving 1cm of the stalks) and the whiskery bits of the roots (leave at least 2 cm of the main root) and wash off any soil. Find a pyrex or similar microwave-proof bowl that will fit one or more beetroot with a plate on top. If the beetroots are too large to fit in the bowl whole, cut them into sections, but they are best cooked whole. Stab the beetroots several times with a sharp knife. Put one or more beetroots into the bowl (don’t add any water) and the plate on top (cling film doesn’t work well) and cook in the microwave on max power for 5 minutes. 

Leave to cool down in the microwave for at least 5 minutes (10 is better) as the beetroots get very hot and make a lot of steam, and they carry on cooking as they cool. Carefully take the bowl out of the microwave (use a towel as it will be hot) and take off the plate. Using a small sharp knife check how soft the beetroot are.  Use a spoon and fork turn over each of the beetroot as they cook most on the bottom. The smallest beetroot (golf ball size) are usually cooked in 5 minutes but anything larger than a tennis ball will probably need to be turned over and put back in the microwave for up to another 5 minutes (if very big). Again, leave for 5-10 minutes to cool down before carefully taking the bowl out of the microwave. 

When cooked, leave them to cool down a bit more (say 15 mins) and then the skins can be rubbed or peeled off. You can leave them to cool down completely and they will keep a day in the fridge like this.  A small amount of intense beetroot juice will be at the bottom of the cooking bowl.  Save this and use this to flavour/colour whatever dish you are making with the beetroot.