Preheat the oven to 350°F. Lightly grease an 8 1/2" x 4 1/2" loaf pan., For the bread: In a small bowl, mix the buttermilk (or yogurt) with the lemon juice and zest (or lemon oil), and set aside., In another bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside., Beat together the butter and sugar until combined. Beat in one egg until absorbed. Scrape the bowl and add 1/4 cup of the dry ingredients., Beat in the second egg. Scrape the bowl and add the remaining dry ingredients, alternating with the buttermilk mixture, until the batter is uniform., Transfer the batter to the prepared pan, and bake for 55 to 60 minutes, until a paring knife inserted in the center comes out clean. Check after 45 minutes and tent with foil if browning too quickly., For the glaze: While the bread bakes, whisk together the glaze ingredients until the sugar dissolves., When the bread is done, remove from the oven and poke it all over with a toothpick or skewer., While the loaf is hot, drizzle the top with the glaze, letting it sink in before pouring more over. When all the glaze is used, let the bread cool on a rack for 15 minutes., After that time, tip the bread out of the pan, and return to the rack to finish cooling completely before slicing. The bread will keep for 5 days on the counter, covered. Freeze for up to 3 months.