Heat the Oven - Preheat the oven to 350°F (177ºC). Grease a 9-by-5-inch loaf pan with nonstick cooking spray or olive oil.
Mix the Yogurt Mixture - In a small bowl, combine the yogurt, chia seeds, 2 tablespoons lemon juice, and 1 tablespoon zest. Set aside.
Mix Dry Ingredients - In a medium bowl, whisk together the flour, baking soda, and salt.
Mix the Egg Mixture - Using a stand mixer fitted with the paddle attachment or hand mixer on high speed, whisk the olive oil and granulated sugar until combined, about 4 minutes. Stir in the vanilla extract. Add the eggs, one at a time, beating well between each addition, scraping down the sides of the bowl as needed.
Make the Batter - Reduce the speed to low and add the dry ingredients in 3 batches, alternating with 2 batches of the chia yogurt mixture.
Bake - Pour batter evenly into the prepared loaf pan and smooth the top with an offset spatula. Bake in the center of the oven until a toothpick comes out clean and the top has set, about 40 to 45 minutes. The internal temperature should reach between 205 to 210°F (96 to 99ºC).If the top begins to brown rapidly towards the final minutes of baking (around 35 minutes), tent the cake loosely with foil, but without touching the surface.
Cool - Cool the cake in the pan for 10 minutes. Carefully remove and transfer to a wire rack to cool completely.
Make the Glaze - In a medium bowl, whisk together the powdered sugar, 2 tablespoons lemon juice, and ½ teaspoon lemon zest. If needed, adjust with more lemon juice or powdered sugar until a glue-like consistency is reached.
Add the Glaze - Drizzle the glaze over the cake, letting it drip down the sides. Sprinkle with ½ teaspoon lemon zest. Let it set before slicing and serving.
Notes
Using All-purpose and Whole Wheat Flour: I found that 3/4 cup white whole wheat flour, plus 3/4 cup all-purpose flour, gave a more tender cake. Make this substitution if you're okay with not having all the whole wheat flour in the recipe.
Substituting the White Whole Wheat Flour: It can be replaced with all-purpose flour, whole wheat flour, or a half-and-half mix.
Using Poppyseeds: Add 1 1/2 to 3 teaspoons in addition to the chia seeds. Alternatively, the poppy seeds can be substituted completely for chia seeds.
Storing: Store in an airtight container for up to 2 days. Wrap and freeze for up to 1 month.