Preheat the oven to 350 degrees Fahrenheit and line a 9x5-inch loaf pan with parchment paper, or grease it lightly.
In a bowl, whisk together the flour, baking powder, and salt.
In a separate large bowl, whisk the sugar, eggs, Greek yogurt, oil, lemon zest, lemon juice, and vanilla until smooth.
Gently fold the dry ingredients into the wet ingredients until just combined.
Toss the raspberries with 1 tablespoon of flour, then carefully fold them into the batter.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 50 to 60 minutes, or until a toothpick inserted in the center comes out clean.
Let the loaf cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.
Whisk the melted butter and powdered sugar together until smooth and thick.
Add 1 tablespoon of lemon juice and mix well, adding a bit more only if needed for a thick, spreadable glaze.
Stir in the lemon zest, if using.
Let the glaze rest for 2 to 3 minutes to thicken, then spread it over the cooled loaf.