Preheat the oven to 350 degrees.
Butter a 6-cup loaf pan. Line the bottom with parchment or waxed paper, pressing it in firmly. Pour the bread crumbs into the pan and shake to coat the sides, then tip out any extra crumbs. In a small bowl, combine the tangerine zest, tangerine juice and lemon juice. Stir and set aside. Sift together the pre-sifted flour, baking soda and salt. In a mixer fitted with a paddle attachment (or using a hand mixer), cream the butter until fluffy. Add the sugar and mix well. Add eggs 1 at a time and mix well. With the mixer running at low speed, add alternating batches of dry ingredients and buttermilk until the batter is just mixed. Add the fruit juice and zest and mix. Pour into the prepared pan and set on a sheet pan. Bake on the sheet pan until the cake is firm in the center and a tester inserted into the center comes out dry and clean (a few crumbs are okay), 70 to 80 minutes.
When the cake is done, let cool in the pan 15 minutes (it will still be warm). Run a knife around the sides of the pan. Set a wire rack on a sheet pan with sides (to catch the glaze) and turn the cake out onto the rack. Peel off the waxed paper. Using a turkey baster or pastry brush, spread the glaze all over the top and sides of the cake and let soak in. Repeat until all of the glaze is used up, including any glaze that has dripped through onto the sheet pan. Let cool at room temperature or, wrapped in plastic wrap, in the refrigerator (well wrapped, the cake will last up to a week). Serve at room temperature, in thin slices.
Glaze: In a bowl, stir the juices and sugar together until the sugar is dissolved.
Courtesy Gale Gand, 'Butter Sugar Flour Eggs' by Gale Gand, Rick Tramonto, Julia Moskin, Clarkson N. Potter Publishers, 1999