I buy it frozen from farmfood £1 for 750g, cook it in the microwave with no additions - May a sprinkle of sweetner to taste after it's cooked. Growing up we used to get a stick straight from the garden and sugar in an eggcup to dip it in!
I do similar, but with orange juice and zest instead of lemon. One orange and a 400g pack of rhubarb does me four servings so that 's still very low carb in my estimation. . I chop mine fairly small and cook it in an open pan with erithritol type sweetener, and a big dollop of butter,which with the orange juice are all it needs liquid-wise and I find it's cooked in about 10-15 mins or so.
I'm surprised that rhubarb isn't often listed with other low carb fruits and veggies, same with gooseberries and black and red currants.
I love the forced rhubarb stewed for a few minutes, put in ramekins and cooled, then make a custard, pour over the top and bake in a Bain Marie until just set ........ delicious