Prepare the buttermilk by combining the lemon juice and milk with the yogurt. Let it rest for 20 minutes and add the beaten eggs and the cold melted butter. Then mix.
In a large bowl put the two flours, sugar, salt, baking soda and yeast. Incorporate also the liquid mixture and mix until you have a homogeneous mixture.
Prepare a baking tray with parchment paper. Transfer everything to a baking tray and level the surface. Cook at 220 ° C for 25-30 minutes.
Let it cool and finally cut into squares. Your cornbread is ready to serve.