Preheat oven to 160°C / 140°C fan forced

To make the crust:

Place the macadamias on a small oven tray and toast for 5 minutes or until golden brown. Allow to cool.Place the cooled macadamia nuts and the rest of the shortbread crust ingredients in a food processor and process until smooth.Spoon the mixture into a lightly greased Le Creuset 26cm Pie Dish. Place in the oven and bake for 10-15 minutes or until just beginning to turn golden brown. Allow to cool.

To make the frangipane filling:

Place the butter in a saucepan and cook over medium heat until nutty-brown. Set aside to cool slightly.Mix all the frangipane filling ingredients together in a bowl. Transfer the mixture into the pie dish. Bake for an additional 30 minutes, or until golden brown and set.Cool completely and top with the rhubarb lattice.

To make the rhubarb lattice:

Using a vegetable peeler, slice the rhubarb lengthways.Place the water, sugar and rose syrup in a small saucepan and bring to the boil. Reduce to a simmer and add 4 slices of peeled rhubarb. Cook until slightly softened, then drain on paper towel. Repeat, until all the rhubarb is cooked. Reduce the remaining syrup.Line up the slices of cooked rhubarb side-by-side on a sheet of greaseproof paper. Fold alternating slices up, and place perpendicular slices over, in a lattice pattern. Repeat until the sheet of lattice is big enough to cover the entire top of the tart.Flip the sheet onto the top of the cooled tart, and peel the parchment away. Trim off any overhang with kitchen scissors. Using a pastry brush, dab the remaining poaching syrup over the lattice to glaze.