Combine raspberries, sugar, and lemon juice in a small saucepan over medium heat. Cook, stirring occasionally, until raspberries break down and sugar dissolves, 3–5 minutes. Strain through a fine-mesh sieve and cool slightly.
Preheat the oven to 250°F/120°C. Line a baking pan with parchment.
In a clean mixing bowl, whip egg whites until foamy, gradually adding sugar. Continue whipping 7–10 minutes until glossy stiff peaks form. Gently fold in powdered sugar for 2 minutes. Spread the meringue into a rectangle or square, leaving a small border.
Bake for 1 hour, then reduce oven temperature to 200°F/95°C and bake for an additional 2 hours. Turn off the oven and let the pavlova cool completely inside with the door slightly ajar.
Whip cream with milk, sugar, and pudding powder until firm. Chill until assembly. Cut fruits to convenient sizes. Just before serving, place cooled meringue on a platter, spread or pipe whipped cream, arrange fruits on top, and drizzle with raspberry coulis. Serve at the center of the table.