First, pop your oven to 350 degrees Fahrenheit. That's nice and cozy for baking. Then, get that loaf pan ready – the 9 by 5 inch one. Just spray the inside with cooking spray so nothing sticks, and line the bottom with parchment paper. This makes getting the loaf out later so much easier.
Now, let's talk seeds! We're using sunflower, pumpkin, flax, and sesame seeds. Toss 'em in a small dry pan over medium heat, stirring constantly. They'll start to smell nutty and maybe even make little popping sounds – just keep going until they're lightly browned, about 5 to 7 minutes. Set aside 2 tablespoons of these toasted seeds in a small bowl for sprinkling on top. Pour the rest into a bigger bowl.
Add the almond flour, coconut flour, baking powder, baking soda, and salt to that big bowl. Give it a good whisk to mix everything up. While you're doing that, crack some eggs into another medium bowl, pour in the buttermilk or yogurt, add some oil, and whisk in the chia seeds and maybe some maple syrup (you can totally skip this if you don't want extra sweetness!).
Now, pour the wet stuff into the dry stuff and stir everything together until it just looks and comes together. Don't overmix! Pour this lovely batter into your prepared pan. Sprinkle the reserved seeds on top and gently press them down a bit so they stick a little. Let it rest for about 10 minutes to set up a bit.
Then, bake it in the preheated oven for about 40 minutes. It's done when the outside is nicely golden brown and a toothpick stuck in the middle comes out clean (no wet batter!). Once it’s done, let it cool in the pan on a wire rack for about 30 minutes. Then, you can carefully turn it out onto the rack to cool completely before slicing and eating! Good luck, I bet it smells amazing while it’s baking.