Step 1: Preheat the Oven and Prepare the Dry Ingredients.

Preheat the oven to 350°F (175°C).

Combine the cake flour and salt. Sift together five times. This is important for creating a light and airy cake. Set aside.

Step 2: Beat the Egg Whites.

Beat the egg whites until frothy (lots of bubbles but still liquidy and loose).

Add the cream of tartar. Beat on high until stiff peaks form.

Step 3: Gradually Add the Sugar.

With the mixer on medium-low speed, slowly sprinkle in the sifted sugar as it mixes in.

Step 4: Fold in the Flour.

Remove the bowl from the mixer.

Gently fold in the sifted flour mixture until it’s all combined. Be careful not to overmix.

Sprinkle the vanilla into the bowl. Fold gently to combine.

Step 5: Bake the Cake.

Spoon the batter into an ungreased tube pan. Smooth the top.

Bake for 35-45 minutes, or until a wooden skewer inserted all the way to the bottom comes out clean.

Don’t open the oven door while it’s baking! This can cause the cake to collapse.

Step 6: Cool the Cake Upside Down.

Carefully remove the cake from the oven.

Immediately invert it onto a wine or vinegar bottle.

Let the cake cool completely while hanging upside down. This prevents the cake from collapsing.

Once totally cool, remove it from the pan.

Step 7: Make the Strawberry Filling.

Sprinkle the jello powder into a bowl.

Pour in 2 1/2 cups of boiling water.

Stir to dissolve the jello.

Add the bag of frozen sliced strawberries. Stir to cool the mixture.

Step 8: Prepare the Cake for Filling.

Turn the cake upside down so that the end that was stuck to the bottom of the pan is now facing up.

With a serrated knife, carefully cut the top 1 inch of cake from the top. Remove it and lay it beside the cake.

Next, with a small paring knife, make two concentric cuts in the cake: one cut is 1 inch from the outside rim, the other cut is 1 inch from the inside rim.

Be careful not to cut all the way through to the bottom of the cake! Leave about an inch from the bottom.

Tear out a trench in between the two cuts. Save the torn cake pieces for another use (cake pops, trifle, etc.).

Step 9: Thicken the Filling (If Necessary).

By now, the strawberry mixture should be cool and somewhat gelatinous.

IMPORTANT: If the mixture is not thick, stick it in the freezer for 15 minutes or until it thickens and sets.

Step 10: Fill the Cake.

Carefully spoon the thickened strawberry mixture into the trench in the cake.

Fill it all the way to the top and even slightly above to allow for a little settling.

Place the top of the cake back on top, lining it up just right.

Step 11: Chill the Cake.

Refrigerate the cake for a couple of hours (or you can stick it in the freezer for an hour or so if you’re in a hurry!).

Step 12: Make the Whipped Cream Frosting.

To serve, whip together the heavy cream and sugar until stiff peaks form.

Step 13: Frost and Serve.

Spread the whipped cream all over the cake.

Cut into slices and serve! Note that once you make a cut, the filling will slightly seep out of the remaining cake, but not overly so.