To make compote, place all ingredients, except strawberries, into a small pot. Bring to a gentle simmer and cook until mixture thickens, and rhubarb is just tender. Add a little more orange juice if liquid in pot overly reduces.
Stir in strawberries, and then remove from heat. Cool to room temperature, and then chill well. Compote can be made a day or two in advance and kept in the fridge.
To make the cake, first preheat oven to 350 degrees F. Lightly grease and flour a 9-inch round cake pan.
In a mixing bowl, cream together butter and sugar, and then mix in eggs, lemon zest and vanilla. Sift together dry ingredients. Mix dry ingredients into wet ingredients alternately with the milk until just combined. Spoon the batter into pan. Bake for 40-45 minutes, or until a toothpick into the centre of the cake pulls out clean.
Cool cake on baking rack 30 minutes, and then carefully pop out of the cake pan onto a wide-sided plate. Brush top with 1/4 of the glaze. Allow it to soak in and then brush with 1/4 more of the glaze. Repeat process until the glaze is all used. Serve wedges of cake with a spoon of compote alongside. Garnish with mint sprigs, if desired.