Beat butter and margarine until fluffy and white. Add in a couple drops of yellow food coloring while keep beating, set aside
Beat yolks, icing sugar, vanilla powder until thickened. Add in butter mixture while keep beating until well combined.
Add in flour mixture and fold lightly and slowly with spatula until well combined
Lay parchment paper on 2 of 20 x 29 cm pan
Pour 1 ladle soup of batter, spreading evenly and bake at 170 C for 10 minutes. Take out pan, turn off oven and turn on broiler. Press cake with flat spatula.
Pour another ladle of batter on top and bake for 5-10 minutes (depending the correct heat of your oven temperature). Turn of broiler and turn on oven, and bake for another 10 minutes.
Do the same with the other pan (so this recipe makes 2 cake roll)
Once cake is cooked, take out from oven and flip on a new parchment paper, peel the previous parchment paper, brush cake with sweetened condensed milk and place one tikar on one cake, roll, wrap on its parchment paper, let cool, then slice.
Do the same with the other cake and tikar.