In 9 or 10 inch springform pan, combine crumbs, melted butter, and 1/4 cup sugar. Press evenly over bottom of pan and halfway up sides. Bake at 375 for 7-8 minutes, no longer.
Cream room temperature cream cheese well, add sugar, and cream until smooth, scraping sides and bottom of bowl frequently to integrate any cream cheese lumps. Cream in sour cream, eggs, flour and vanilla. When smooth once more, stir in lime juice. Note: 3/4 Cup of Key Lime juice makes a very tart cheesecake. If you prefer a less tart cheesecake, start with 1/3 cup and increase to taste.
Pour over prepared crust. Return to 375 oven for 15 minutes. Lower temperature to 250 and continue baking 50 minutes for 10 inch pan, 55 minutes for 9 inch pan. Cool on wire rack IN PAN for 20 minutes. Run a sharp knife around edge to loosen cheesecake, but do NOT remove from pan. Refrigerate at least 6 hours before serving. May be garnished with sweetened whipped cream, lime zest, or both.