Add raspberries, sugar, and lemon juice to a saucepan.

Cook over medium heat 5–7 minutes until juicy.

Stir in cornstarch slurry; cook 1–2 minutes until thickened.

Strain if you want a smooth filling.

Cool completely.

Preheat oven to 350°F.

Mix cake mix, pudding mix, sour cream, melted butter, water, and eggs: 30 seconds on low, 2 minutes on medium

Stir in white chocolate chips.

Pour half the batter into a greased bundt pan.

Spoon cooled raspberry filling around the center (avoid the edges!). Swirl gently.

Add remaining batter on top and repeat.

Bake 40–45 minutes or until a skewer comes out clean.

Cool 5 minutes → loosen edges → flip onto wire rack.

Cool fully before frosting.

Beat all frosting ingredients 3–5 minutes until smooth and thick.