Place the lime, raspberries and sugar in the bottom of a rocks glass (short thick-walled glass). Muddle them together well to get lots of juice out of the lime and break up the raspberries.
Add the cachaca to the glass then either transfer to a shaker with some ice and shake well, or add ice to the glass and stir to mix and cool.
Pour the mixture into a rocks glass to serve, topped up well with crushed ice.
Notes
Typically this would be serve unstrained, but you can strain the drink if you prefer. If you prefer a sweeter drink, you can add a little more sugar.