Preheat oven to 190ºC .
Combine butter and 1- half cups sugar. Beat with mixer until well blended. Beat in eggs and mix until smooth. Add thyme, orange peel, flour and baking powder; mix well.
Put remaining quarter cup sugar into a shallow bowl.
Shape dough into 2 cm balls (chill dough to make this step easier).
Roll balls in sugar to coat, and place on ungreased baking sheet.
Bake at 190ºC . until edges are brown, about 12-15 minutes.
Remove from baking sheet and cool on racks.
Makes about 5 dozen.