How to Make It
Preheat the oven to 350°. In a medium bowl, whisk the flour with the baking powder and salt. In a bowl, using a handheld electric mixer, beat the butter with the sugar until light and fluffy. Add the egg and beat well. Gradually add the flour mixture and beat until incorporated, then stir by hand to blend thoroughly.
Scrape the dough into a 9-inch tart pan with a removable bottom. Using a piece of plastic wrap, pat the dough into the pan in an even layer. Bake for about 20 minutes, or until the pastry is firm and golden brown. Transfer to a rack to cool completely. Leave the oven on.
Spread the sliced almonds on a baking sheet and toast in the oven for about 4 minutes, or until golden brown.
In a small saucepan, cook the sugar and butter over low heat, stirring, until the mixture turns light brown, about 3 minutes. Slowly add the milk and cook, stirring, until the mixture is smooth. Remove the pan from the heat and stir in the sliced almonds. Spread the topping over the tart base and bake for 10 minutes, or until sizzling and set. Let cool slightly. Cut the tart into wedges and serve warm or at room temperature.