In a stand mixer, cream together the very soft unsalted butter and powdered sugar until smooth and fluffy, about 3–5 minutes.

Add in an egg, followed by the almond meal and optional orange zest, mixing until well combined.

Gradually incorporate the plain flour and salt until the dough forms a ball.

Chill the dough for at least 1 hour to firm up.

Preheat your oven to 325°F (160°C).

On a lightly floured surface, roll out the chilled dough to about 1/8-inch thickness.

Line a tart pan with the rolled-out pastry, press gently into the corners and trim any excess.

Dock the base with a fork and blind bake for 25–30 minutes until golden.

Allow the pastry shell to cool completely before filling.

In a saucepan, heat the orange juice over medium heat until simmering.

In a bowl, whisk together eggs, caster sugar, and cornstarch until smooth.

Gradually whisk the hot juice into the egg mixture and return to the pot.

Stir over medium heat until thickened, about 5–7 minutes.

Remove from heat.

If using gelatin, dissolve in warm water and stir into the thickened mixture.

Mix in the softened butter and reserved orange zest until smooth.

Pour the orange cream filling into the cooled tart shell, smoothing the top.

Cover with plastic wrap and refrigerate for 2–3 hours or up to 24 hours.

Once set, slice into wedges to serve.

Garnish with fresh orange segments or mint leaves.