Preheat your oven to 350°F and grease a 9x5-inch loaf pan really well (I use cooking spray so nothing sticks). Line the bottom with parchment paper for extra insurance. Whisk together your 3 cups flour, 1 teaspoon baking powder, and 1/2 teaspoon salt in a separate bowl and set aside.

Cream together your softened 1/2 cup butter and 1 cup sugar using an electric mixer on medium speed until it's light and fluffy—this takes about 3 minutes and you'll see the color get lighter. Don't skip this step because it helps create that tender crumb you're after.

Add your 4 eggs one at a time, beating well after each addition so they incorporate smoothly. Pour in your 1 teaspoon vanilla bean paste and mix until you don't see any streaks of it left in the batter.

Now alternate adding your flour mixture and 1 cup milk to the batter, starting and ending with the dry ingredients. Mix on low speed after each addition—about 3 additions of flour and 2 of milk—until just combined. Don't overmix or the cake gets tough (trust me on this).

Toss your 1 1/2 cups fresh peach slices with the 2 tablespoons honey and 1 teaspoon lemon zest in a small bowl so they're lightly coated. This keeps them from sinking straight to the bottom, and also the honey helps them stay juicy while the cake bakes.

Fold the peaches and 1/4 cup walnuts into the batter gently using a rubber spatula—maybe 10 to 12 folds until everything's just mixed in. Pour this into your prepared pan and smooth the top with the back of a spoon.

Bake at 350°F for 50 to 55 minutes until a toothpick inserted in the center comes out with just a few moist crumbs (not wet batter). The top should be golden brown and the kitchen smells absolutely amazing by this point. Let it cool in the pan for 15 minutes, then turn it out onto a wire rack to cool completely.