Mix crust ingredients together into a ball, wrap loosely with a damp towel, and chill for about 30 minutes to make dough less crumbly.
Preheat oven to 160ºC/325ºF. Press the chilled crust dough into the bottom of a pie dish. Pre-bake until slightly toasted, about 10 minutes.
For the filling, stew rhubarb pieces in orange juice and honey, bringing to a boil and then lowering to a simmer until the reduction is slightly thickened. Add a pinch of cornflour/starch to thicken even more, if necessary.
To make the meringue, whisk (you can do this by hand, but an electric mixer will be much quicker) room temperature egg whites in a very clean bowl—any trace of grease will make the job a lot harder, so avoid plastic. Once the mixture starts to become foamy and airy, add the sugar a little bit at a time and just a small squeeze of lemon juice, continuing to whisk until soft or stiff peaks are formed, depending on your preference.
Spread the meringue evenly on top of the pie, starting at the edges and filling in towards the centre. Give it a final swirling flourish and return to the oven and bake for 10-15 minutes or until the meringue is crisp and turning golden. Let it dry out thoroughly after turning off the heat, letting it dehydrate with the oven door cracked as it cools. Serve within the same day.