Heat the blackberries with 2 teaspoons of water in a medium-sized pot over medium heat, stirring occasionally until they soften and break apart. Lower the heat and simmer for 15 minutes. Remove 2 teaspoons of blackberry reduction and set it aside. Stir in the sugar, honey, and lemon juice and continue simmering over low heat until thickened, about 20 minutes, stirring every 5 minutes. Remove from heat, stir in lemon zest and cardamom, and let cool to room temperature then refrigerate.

In a small bowl, whisk together cornstarch and lemon juice until combined. Set aside.

Preheat the oven to 250°F. In the bowl of an electric mixer, beat egg whites at low speed, gradually increasing to medium. When soft peaks form, add sugar 2 tablespoons at a time. Continue beating until glossy peaks form, about 15 minutes.

Add cornstarch mixture to meringue and beat for 1 minute. Fold in vanilla extract and ground cardamom.

Trace an 8-inch circle on parchment paper, flip it upside down on a baking sheet. Dab meringue on corners to secure parchment, then spread remaining meringue into an 8-inch circle.

Bake for 90 minutes at 225°F until crisp, then turn off oven and let cool for several hours.

If cracks form, gently press back into place before topping.

Beat whipping cream, sugar, and cardamom until fluffy and smooth, adding lemon zest, blackberry reduction, and vanilla, then beat until combined.

Place the pavlova on a serving plate. Spread blackberry whipped cream, then blackberry jam on top. Garnish with fresh blackberries, blueberries, and honey. Serve immediately.