Preheat your oven to 350°F and generously grease a 9x13 inch baking dish with butter or cooking spray. While the oven preheats, cut the rhubarb into 1-inch pieces and measure out all your ingredients. Having everything ready before you start mixing will keep the batter from sitting too long and losing its leavening power.

In a medium bowl, toss the prepared rhubarb with the strawberry jello powder until the rhubarb pieces are evenly coated. This allows the jello to begin absorbing the rhubarb's moisture and will create a beautiful pink color throughout the cake layers. Set this mixture aside—it doesn't need to sit long, just a minute or two is fine.

In a large bowl, cream together the softened butter and sugar until light and fluffy, about 2-3 minutes. Add the eggs one at a time, beating well after each addition, then stir in the sour cream and vanilla extract until fully combined. In a separate bowl, whisk together the flour, baking powder, and baking soda. Fold the dry ingredients into the wet ingredients until just combined—don't overmix, as this keeps the cake tender. I find that using sour cream instead of regular milk gives the cake a more tender crumb and richer flavor.

In a small bowl, combine the brown sugar, 2 tablespoons sugar, cinnamon, and nutmeg. In another small bowl, finely chop the nuts into roughly 1/4-inch pieces. Set both mixtures aside until assembly. This step takes just a minute but ensures you're not fumbling with multiple ingredients during assembly.

Spread half of the cake batter from Step 3 evenly into the prepared baking dish. Layer the rhubarb-jello mixture from Step 2 over the batter, then sprinkle with half of the cinnamon-sugar mixture from Step 4 along with the chopped nuts. Carefully spread the remaining batter over the top, trying to cover as much of the fruit as possible—this prevents the cake from drying out. Sprinkle the remaining cinnamon-sugar mixture on top. I like to use an offset spatula dipped in water when spreading the second layer of batter, as it helps you cover the filling without dragging it into the batter.

Bake in the preheated 350°F oven for 45 minutes, or until a toothpick inserted into the cake portion (avoiding the fruit) comes out clean or with just a few moist crumbs. The top should be golden brown. Allow the cake to cool in the pan for at least 10 minutes before serving—this lets the layers set so you get clean slices with all the beautiful layers intact.