Preheat oven to 325°F (160°C). Grease a loaf or cake pan generously with cooking spray and set aside.
Peel the plantains, slice them, and then puree them in a food processor or blender until thoroughly mashed. Set aside.
Combine flour, salt, baking powder, and baking soda. Set aside.
Cream butter and sugar on high in a stand mixture until fluffy and looking white. It takes 3-4 minutes. Then add the yogurt and mix for a minute more.
Stir in the eggs, one at a time, beating well between each addition. Then add the plantain puree and mix until combined.
Sift the dry ingredients into the batter, a little at a time. Then add the grated lime zest, nutmeg, and milk.
Stir well until everything is fully combined, scraping the sides of the mixing bowl as you go.
Pour the cake batter into the greased loaf pan (or cake pan).
Bake at 325℉ (160℃) until a tester inserted into the middle of the loaf comes out clean, 45–50 minutes. Transfer it to a wire rack and allow it to cool.