Preheat your oven to 325°F (160°C), and place cupcake liners in each cavity of your cupcake pan.
In a large bowl, whisk together the flour, cornstarch, baking powder, baking soda and sea salt.
Place all the wet ingredients in the container of a blender, and mix on low until smooth. Whisk the wet ingredients into the dry ingredients until smooth and then stir in the praliné grain. Do not overmix.
Using a large ice cream scoop, fill each liner ⅔ of the way. Gently tap your cupcake pan against your countertop to remove any air bubbles in the batter.
Bake for 25 to 30 minutes on the middle rack, or until a toothpick inserted in the middle comes out clean. Let the cupcakes cool down in the pan for 5 minutes before transferring them to a wire rack to cool completely.
Raspberry curd
In a small saucepan, whisk together the sugar and cornstarch. Whisk in the lemon juice until you get a lump-free slurry. Add the raspberry puree and stir it in.
Cook on medium heat while whisking continuously until it starts to bubble and thicken. Remove from the heat and whisk in the margarine until homogenous.
Cover the mixture with plastic film, making sure that the wrap touches the whole surface of the curd. Once cold, whisk the curd to loosen it and transfer in a small pastry bag with a small opening.
Using the paddle attachment, mix the peanut butter and buttercream together until smooth. Let the mixer run on low for 2 minutes to remove any air bubbles. Transfer into a large piping bag with a Wilton 6B pastry tip.
Assembly
Starting from the center, pipe a shallow rosette of buttercream, and in the same movement, pipe a second layer of buttercream in a donut shape on top of each cupcake. Lightly sprinkle some praliné grain on top of the buttercream.
Fill the middle of the buttercream ring with the raspberry curd. Enjoy!
Notes
Buttercream: Depending on your mixer, you might need to make a half recipe or full recipe of buttercream and then store the excess.