Zest lemon and make custard Zest up to whole lemon, then halve. In a large baking dish, whisk together milk, vanilla, cinnamon, 2 eggs, and 1⁄4 teaspoon salt to combine (doing this in a baking dish, rather than in a bowl, helps the brioche soak evenly and all at once).
Soak brioche and make lemon mascarpone Add brioche slices to baking dish with custard in a single layer. Let soak on 1 side, 2 minutes, then flip and soak 2 minutes more (see recipe tip). Transfer to a plate and set aside for Step 5. Meanwhile, in a small bowl, stir together mascarpone, lemon zest (if using), and half of powdered sugar to combine. Set aside until ready to serve.
Make raspberry syrup In a small pot, whisk together raspberry preserves, 1 squeeze lemon juice, 1⁄3 cup water, and 1⁄4 teaspoon salt. Bring to a boil over high heat, then reduce heat to medium high; simmer, stirring occasionally, until syrupy, 5–6 minutes. Remove pot from heat; cover to keep warm until ready to serve. Use remaining lemon to brighten a glass of water.
Make candied almonds Place almonds in a large nonstick pan over medium-high heat. Toast, stirring, until light golden, 2–3 minutes. Add turbinado sugar and cook, stirring frequently, until sugar begins to melt and cling to almonds, 2–3 minutes more. Add 1⁄8 teaspoon salt; cook, stirring vigorously, to coat, 1 minute more. Remove pan from heat. Transfer almonds to a plate; set aside to cool. Rinse pan and wipe clean for the next step.
Cook pain perdu Return pan from almonds to medium- high heat with 2 teaspoons canola oil. When oil is shimmering, add soaked brioche in a single layer. Cook, working in batches and adding oil in between as needed, until golden on bottom, 2–4 minutes. Flip, reduce heat to medium, and cook until golden brown, 3–5 minutes more. Remove pan from heat.
Plate pain perdu Divide pain perdu among serving plates. Dollop over lemon mascarpone. Drizzle over raspberry syrup and garnish with candied almonds. Dust with remaining powdered sugar (see recipe tip). Enjoy!
Be sure to read through the entire recipe before you begin cooking. The skin of the lemon (and other citrus fruits) is home to the highest concentration of aromatic oils, so chefs use zest to add bright flavor and a little texture. It's easier and safer to zest the lemon before cutting and juicing. If you don't have a zester, no worries—your mascarpone will still taste delicious! Pay careful attention to how long the bread has been soaking. Waiting too long could cause it to become soggy. Place powdered sugar in a fine-mesh sieve and shake gently over the pain perdu for the perfect light dusting. If you don't have a fine-mesh sieve, feel free to use a spoon for sprinkling.