Preheat the oven to 325°F (165°C). Position a rack in the center of the oven. Grease a 9x5-inch (standard) loaf pan with the 1 tsp melted butter and line the bottom with a strip of parchment for easier removal, if desired.

Dry ingredients

In a medium bowl, whisk together the 2 cups all-purpose flour, 1 tsp baking powder, and 1/2 tsp salt until evenly combined. Set aside.

Cream butter and sugar

In a large mixing bowl, beat the 1 cup softened unsalted butter on medium speed until smooth and slightly pale, about 1–2 minutes. Add the 1 cup granulated sugar and continue beating on medium-high until light and fluffy, about 3–4 minutes, scraping the bowl once or twice.

Add eggs and vanilla

Add the 4 large eggs, one at a time, beating well after each addition so the mixture remains emulsified. Scrape the bowl as needed. Stir in the 2 tsp vanilla extract.

Combine batter

With the mixer on low, add about one-third of the dry ingredients and mix until just combined. Add half of the 1/4 cup whole milk and mix briefly. Add another third of the dry ingredients, then the remaining milk, then finish with the remaining dry ingredients. Mix only until there are no visible streaks of flour; do not overmix.

Transfer and smooth

Scrape the batter into the prepared loaf pan and smooth the top with a spatula. Tap the pan gently on the counter 2–3 times to release large air bubbles.

Bake

Bake in the preheated 325°F (165°C) oven for 55–70 minutes, or until the top is golden and a toothpick inserted into the center comes out with a few moist crumbs (not wet batter). If the top browns too quickly, loosely tent with aluminum foil for the last 15–20 minutes of baking.

Cool

Remove the pan from the oven and let the cake cool in the pan on a wire rack for 10–15 minutes. Run a knife around the edges, invert onto the rack (use the parchment strip if used), then turn right-side up and let cool completely, about 1–1.5 hours.

Optional Finish

Once the cake is fully cooled, lightly dust the top with the 1 tbsp confectioners' sugar using a fine-mesh sieve or sifter. Slice into 8–10 pieces and serve.