Preheat the oven
to 350°F/180°C/gas 4. Line three cookie sheets with
parchment paper.
Sift the flour, baking soda, and
salt into a medium bowl. Stir in the sunflower
seeds.
Beat the butter, 2 cups (400 g) of sugar,
oil, and grated zest of 1 lime in a large bowl
with an electric mixer at high speed until
creamy.
Add the eggs,
beating until just blended. Mix in the dry
ingredients and lime juice. Mix the remaining sugar
and lime zest in a small bowl.
Form the dough
into balls the size of walnuts and roll in the lime
sugar. Place the cookies 2 inches (5 cm) apart on
the prepared cookie sheets, flattening them
slightly.
Bake, one sheet
at a time, for 10-12 minutes, or until just golden
at the edges. Transfer to racks and let cool
completely.