1. Preheat oven to 350°.
2. Place butter and all but 1 teaspoon sugar in a bowl; beat with a mixer at medium speed until light and fluffy (about 5 minutes). Add egg; beat until well combined.
3. Heat milk in a small pot over medium heat. Crush saffron with remaining 1 teaspoon sugar in a mortar or small dish. Remove milk from heat; add saffron sugar to pot, and stir. Cover and let steep 5 minutes.
4. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, and salt in a bowl.
5. Add flour mixture and milk mixture alternately to sugar mixture, beginning and ending with flour mixture, blending well after each addition. Stir in raisins.
6. Scrape batter into a lightly greased 8-inch round cake pan. Arrange almonds on top of batter; sprinkle evenly with pearl sugar.
7. Bake at 350° for 25 minutes or until tester inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove cake from pan. Cool completely on wire rack.
Learn About Saffron: These yellow-orange stigmas from a small purple crocus make up the world's most expensive spice because it is extremely labor-intensive--each flower provides only three stigmas, which must be hand-picked then dried. Fortunately, a little saffron goes a long way. This spice is integral in many traditional dishes such as the Swedish saffron buns mentioned, risotto milanese, bouillabaisse, and paella. Powdered saffron loses its flavor and can often be adulterated with imitations. Buy a small quantity of high-quality threads, and crush or steep just before using. Store saffron airtight in a cool, dark place.