Prepare the Poached Peaches: In a medium saucepan, combine the water, granulated sugar, and lemon juice. Bring to a simmer over medium heat, stirring until the sugar is completely dissolved.

Gently place the peeled and halved peaches into the simmering syrup. Reduce heat to low, cover partially, and poach for 10-15 minutes, or until the peaches are tender but still hold their shape. Remove from heat and let cool completely in the syrup.

Prepare the Raspberry Sauce: While the peaches cool, combine the raspberries, powdered sugar, and lemon zest in a small saucepan. Heat over medium-low heat, stirring occasionally, until the fruit breaks down and the sauce thickens slightly (about 5-7 minutes).

Strain the raspberry sauce through a fine-mesh sieve into a bowl, pressing on the solids with the back of a spoon to extract all the liquid (the coulis). Discard the seeds. Chill the sauce thoroughly.

Assemble the dessert: Place one or two peach halves in a dessert bowl. Top generously with one scoop of vanilla bean ice cream.

Spoon a generous amount of the chilled raspberry coulis over the ice cream and peaches. Garnish with toasted sliced almonds and serve immediately.