Pre-heat oven to 350F/ 175C. Grease and line a 13X9" baking pan with parchment paper. Leave extra paper hanging on the side so that it's easy to lift up the cake later.
In a bowl, patiently beat the butter and sugar together for 3-4 minutes till light and fluffy. If using a stand mixer, use the paddle attachment or else just use a hand mixer.
Add the eggs one at a time, beating well after every egg to make sure its combined well into the mixture. Also stir in the vanilla extract and baking powder.
Alternate between adding the flour and milk and mix until just combined. Alternating the dry and wet ingredients means that you add ⅓ of the flour first, mix and add half the milk; mix and then add ⅓ of the flour again, mix add the remaining milk and then the flour. This helps incorporate everything well and avoids over mixing.
Pour the mixture into the prepared baking tin and bake for approximate 45 minutes or till a toothpick inserted into the middle of the cake comes out clean. Once the cake is baked, let it cool for 15 minutes.
In the meanwhile, prepare the jello according to package instructions.
Once the cake is cooled, poke the cake with the back of wooden spoon or thick skewer and make holes in the cake at every inch. Pour the jello into the holes and refrigerate the cake for 3-4 hours.
An hour before serving, spread whipped cream over the cake and decorate with strawberries slices. Refrigerate again for an hour or till ready to serve. This cake keeps well in the refrigerator for 2-3 days.