In a medium saucepan, combine 2 cups of frozen raspberries, ¾ cup of granulated sugar, and 2 tablespoons of lemon juice over medium heat. Stir until it begins to bubble, then lower heat and let it simmer for 23-25 minutes, stirring occasionally, until it thickens. Remove from heat and allow it to cool completely.

In another small saucepan, bring 1 cup of water to a boil and add ½ cup of sugar along with 1 cup of raspberries. Let it boil for 1 minute, then reduce to a simmer for 3 minutes. Remove from heat, strain the syrup through a fine mesh sieve, discarding solids, and let it cool at room temperature.

In a large mixing bowl, use a hand mixer to beat 1 cup of cold mascarpone cheese, ½ cup of powdered sugar, the juice from ½ a lemon, and 1 teaspoon of vanilla paste until fully combined. In a separate bowl, whip 1 cup of heavy cream until medium-stiff peaks form. Gently fold the whipped cream into the mascarpone mixture until well blended.

Grab a 9x9-inch baking dish and start by spooning in a layer of the mascarpone cream. Quickly dip ladyfinger cookies into the cooled raspberry syrup and layer them on top of the cream. Spread half of the prepared raspberry jam over the ladyfingers, followed by another layer of the mascarpone filling. Repeat the process, finishing with the remaining mascarpone layer.

Cover the assembled Fresh Raspberry Tiramisu with plastic wrap and place it in the refrigerator. Allow it to chill for at least 8 hours, or ideally overnight.

Just before serving, spread any remaining raspberry jam over the top of the Tiramisu for a glossy finish. Optionally, garnish with fresh raspberries and lemon slices.