Cream the butter and sugar together in a mixer bowl with a paddle attachment. Mix until creamy and throughly incorporated. Make sure to scrape sides and mix for a few more seconds.
Add eggs slowly and mix.
Add vanilla extract and mix.
In a separate bowl, mix the salt and flour and slowly begin to add the flour mixture to the mixer bowl on low speed. Make sure to scrape sides.
Once fully mixed, add the food colors.
Lastly add the poppy seeds and mix.
Wrap in clear plastic wrap and store in the fridge for 30-60 minutes.
Bake at 350ºF/176ºC for 12 minutes rotating the pan at the 6 minute mark for an even bake.