Place angel food cake onto serving platter. Slice evenly into 3 layers. Set aside.: The top note you will notice is the soft, pillowy texture under your knife, with a faint sweet scent that promises a delicate bite. Take care to use a long serrated knife and a gentle sawing motion to avoid tearing, keeping the slices as even as possible so the cake stacks straight. Pressing too hard will compress the crumb and ruin the cloud like lightness, so steady hands matter here. If the cake resists, chill it briefly for cleaner cuts. Watch for crumbs falling into the platter, and gently brush them away so the presentation stays tidy.
In a large bowl, whisk pudding mix and cold milk together for 2 minutes until smooth and thickened. Fold in cool whip. Spread about 1 cup of this mixture over top the 1 st layer of angel food cake. Top with 2 nd layer of cake, another cup of lemon cool whip mixture and the top layer of cake.: You will hear a soft whisking rhythm and see the powder dissolve, then the mix will change from runny to glossy and slightly thick, smelling of lemon. The cold milk helps the pudding thicken properly and folding in the fat free cool whip preserves airiness, so use a spatula and lift gently to keep volume. Over stirring can deflate the mixture and lead to a heavy filling, so stop once streaks disappear and the texture feels light but stable. If lumps remain, let it sit for a minute and whisk again gently to avoid breaking down the whipped texture.
Use remaining lemon cool whip mixture to frost the outside of the cake and top with raspberries. Dust with powdered sugar, if desired. Refrigerate until ready to serve.: As you spread the filling, you will feel a slightly resistant, billowy texture that smooths into place; the lemon aroma will become more pronounced. Use an offset spatula or the back of a spoon and apply gentle pressure to coax the mixture to the edges, creating a uniform layer that will support the next cake tier. If you pile too much in one spot the cake may slide later, so aim for even distribution. A common slip is using a cold cake slice straight from the fridge which can make the filling firm up unevenly, so keep everything at the same chill level for better adhesion.
Top with 2 nd layer of cake, another cup of lemon cool whip mixture and the top layer of cake.: When stacking, the faint springy give of each layer should nestle into the filling and create a cohesive height, while the lemon scent intensifies. Align the edges carefully to maintain a round silhouette, and press each layer down lightly so the filling settles but does not squeeze out. If layers are crooked, slide them gently into place rather than forcing, which could tear the cake. Avoid pressing too firmly or the structure may compress and lose its light texture.
Use remaining lemon cool whip mixture to frost the outside of the cake and top with raspberries.: The frosting stage allows you to shape the dessert visually; as you spread the filling over the sides, notice how the cake takes on a smooth, pale lemon coat and the subtle creamy aroma becomes comforting. Place raspberries with intention, clustering some at the top and scattering a few along the base for balance. Keep movements soft and patient to preserve the cake's surface. A typical error is overworking the frosting which leads to streaks and loss of that soft, cloud like finish, so do small, confident strokes and step back to assess.
Dust with powdered sugar, if desired. Refrigerate until ready to serve.: The final dusting adds a whisper of sweetness and a tiny visual snow that compliments the berries. Refrigeration firms the filling so slices hold their shape and the lemon flavor chills into a refreshing note. Expect a subtle condensation on the surface as it chills, which is normal, but avoid leaving it out too long at room temperature or the filling can soften and run. When storing, cover loosely with a tented foil to protect the raspberries and keep the cake from absorbing other fridge odors.